Speaking amid reports that Washington and its allies are preparing to launch a punitive cruise missile strike on Syrian targets, US Secretary of State John Kerry accused Bashar al-Assad´s regime of engaging in a cover-up.[break]
"Let me be clear. The indiscriminate slaughter of civilians, the killing of women and children and innocent bystanders by chemical weapons is a moral obscenity," Kerry declared in a televised statement.
"By any standard it is inexcusable, and despite the excuses and equivocations that some have manufactured, it is undeniable."
Kerry said Washington would provide more evidence of who was behind the attack, and that US President Barack Obama was determined the guilty would face consequences.
"We have additional information about this attack, and that information is being compiled and reviewed together with our partners, and we will provide that information in the days ahead," he warned.
"Make no mistake. President Obama believes there must be accountability for those who would use the world´s most heinous weapons against the world´s most vulnerable people. Nothing today is more serious."
Kerry was speaking as UN inspectors met survivors of last week´s attack, which the independent medical agency Doctors Without Borders has said left at least 355 people dead from "neurotoxic symptoms."
The UN convoy came under sniper fire as it tried to approach the Damascus suburb where the attack was reported, but the team nevertheless managed to visit victims receiving treatment in two nearby hospitals.
"It was a very productive day," UN spokesman Farhan Haq told reporters, adding that the team, led by Swedish expert Ake Sellstrom, is "already gathering valuable evidence."
UN leader Ban Ki-moon said that despite the "very dangerous circumstances" the investigators "visited two hospitals, they interviewed witnesses, survivors and doctors. They also collected some samples."
The UN team was in a buffer zone between government and opposition-held areas when it came under attack.
Ban said the United Nations had made a "strong complaint" to the Syrian government and opposition forces. The rebels and Assad´s government traded blame for the sniper assault just as they did the chemical attack.
The United States accused Syrian government forces of resuming their shelling of the attack site soon after the UN team departed in a bid to destroy evidence.
President Vladimir Putin of Russia -- a staunch Assad ally that provides the regime with diplomatic cover by blocking UN Security Council action -- meanwhile remained unimpressed by the mounting evidence of an atrocity.
Putin on Monday told British Prime Minister David Cameron there was no proof Damascus had used chemical weapons, according to Cameron´s office.
Cameron cut short his holiday on Monday to return to London to plan a response. Britain, along with France, has been in the forefront of demands for tougher action against Assad´s regime.
A senior Israeli delegation meanwhile visited the White House for high-level talks on the Syrian crisis and the showdown over Iran´s controversial nuclear program.
The Syrian opposition says more than 1,300 people died when toxic gases were unleashed on Eastern Ghouta and Moadamiyet al-Sham, two neighborhoods on the outskirts of Damascus.
Syria approved the UN inspection on Sunday, but US officials said it was too little, too late, arguing that persistent shelling had "corrupted" the site.
The inspection came as the West appeared to be moving closer to launching a military response, after officials confirmed the US Navy has four warships armed with cruise missiles on standby in the eastern Mediterranean.
With China and Moscow expected to boycott any resolution backing a military strike, British Foreign Secretary William Hague said the West could act even without full UN Security Council backing.
There is also precedent for Obama to act militarily without US congressional backing, despite a law technically requiring it.
The alleged poison gas attack is only the latest atrocity in a conflict that has claimed more than 100,000 lives since March 2011.
Assad, in an interview with a Russian newspaper published Monday, denied accusations his government was behind the attack, calling the charges an "insult to common sense."
"The United States faces failure just like in all the previous wars they waged," he added.
Russian Foreign Minister Sergei Lavrov meanwhile warned of the "extremely dangerous consequences of a possible new military intervention" and said intervening without a UN Security Council resolution would be illegal.
Experts believe the most likely US action would see sea-launched cruise missiles target Syrian military installations and artillery batteries deemed complicit in the chemical weapons attack.
US postpones meeting with Russia on Syria: official
WASHINGTON, Aug 27: The United States on Monday postponed a meeting with Russia on the Syrian crisis, as Washington appeared to be positioning for a potential military strike.
"Given our ongoing consultations about the appropriate response to the chemical weapons attack in Syria on August 21," Washington has decided to postpone Under Secretary Wendy Sherman and Ambassador Robert Ford´s meeting with a Russian delegation that was scheduled for this week in the Hague, a senior State Department official said.
"We will work with our Russian counterparts to reschedule the meeting. As we´ve long made clear - and as the events of August 21 reinforce - it is imperative that we reach a comprehensive and durable political solution to the crisis in Syria," the official stressed.
The United States said Sunday there was "very little doubt" Syrian forces had used chemical weapons on civilians, and dismissed an offer by Damascus for a UN team to view the attack site.
The comments marked a significant escalation of a showdown over the horrific attack outside the Syrian capital that killed up to 1,300 people last week, according to the Syrian opposition, and came as Washington appeared to be positioning for possible military action.
Officials said President Barack Obama, who held crisis talks Saturday with top aides, would make an "informed decision" about how to respond to an "indiscriminate" chemical weapons attack.
An official told AFP that based on the reported number of victims and their symptoms, and US and foreign intelligence, "there is very little doubt at this point that a chemical weapon was used by the Syrian regime against civilians in this incident."
The official, speaking on condition of anonymity, said that Washington had noted that Syria had offered to let UN inspectors view the site of the alleged attack on Monday, but said it was too little, too late, and that the evidence available at the site "has been significantly corrupted" due to the delay.
A US diplomatic offensive led by Secretary of State John Kerry, comments coming from the White House and signs the Pentagon is positioning ships closer to Syria fueled an impression that Obama may be getting ready to jettison his antipathy to new Middle Eastern entanglements and order a limited military strike.
No proof yet of Syria chemical attack, Putin tells Cameron
LONDON, Aug 27: Russian President Vladimir Putin on Monday told British Prime Minister David Cameron that there was no evidence yet that the Syrian regime had used chemical weapons against rebels, Cameron´s office said.
During a telephone call between the two leaders, Putin said that "they did not have evidence of whether a chemical weapons attack had taken place or who was responsible", according to a Downing Street spokesman.
Cameron insisted that there was "little doubt" Bashar al-Assad´s regime had carried out a chemical attack, according to a readout of the telephone conversation.
The British leader doubted that the rebels had the capability to carry out such an attack and pointed out that the regime had launched a heavy offensive in the area in the days before and after the incident.
"The regime had also prevented UN access in the immediate aftermath, suggesting they had something to hide," he told Putin.
However, the pair did both repeat their commitment to an agreement reached by G8 leaders in June, which resolved that no-one should use chemical weapons and any use would merit a serious response from the international community.
Russian news agency Ria-Novosti, quoting the Kremlin press office, said that the conversation had "focused mainly on the situation in Syria against the backdrop of media reports on the possible use of chemical weapons near Damascus".
Western nations have upped the rhetoric since reports that chemical weapons were used last week and Britain maintains there is evidence suggesting the regime was responsible.
Cameron already spoke with US President Barack Obama over the weekend to formulate a response to the escalation in the 29-month-old Syrian conflict.
Foreign Secretary William Hague said an international response was possible without the formal backing of the United Nations.
Russia, also a veto-wielding member of the UN Security Council, has repeatedly warned Washington and its allies against military action in Syria.
Syrian President Assad has denied using chemical weapons and warned Monday that any Western strikes against his regime would be doomed to failure.
Moscow, which has backed him throughout the crisis, urged Washington not to preempt the results of the UN inspection and warned that any military action would be a "tragic mistake".
Cameron´s office said the British government would decide on Tuesday whether to recall lawmakers to debate the situation sooner than September 2, when the House is currently due to return.
The prime minister has cut short his holiday to deal with the crisis, and will chair his National Security Council (NSC) on Wednesday.
The NSC, which meets weekly, comprises 10 high-ranking government ministers. Other cabinet ministers plus defence and intelligence chiefs attend when required.
Meanwhile, the Guardian newspaper reported on Tuesday that two commercial pilots had seen C-130 transport planes and picked up fighter jets on their radars flying towards Britain´s Akrotiri airbase in Cyprus.
Former prime minister Tony Blair, who controversially led Britain into the 2003 Iraq invasion, on Tuesday called for action.
Writing in the Times, he warned against the "impulse to stay clear of the turmoil" saying that without action, Syria would become "mired in carnage".
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