Bimal Rana was scored the only goal of the match in the 62nd minute that guided the departmental giant into the last four.
In the semifinal, Army will face the winner of the match between Dharan FC and FAO Academy of Orissa, India slated for Tuesday.
Bimal headed the match winning goal from the danger zone off Santosh Tamang's corner kick.
Army could have doubled the tally if Bharat Khawas's powerful shot from inside the box had not rebounded hitting the top bar just two minutes later.
Army goalie Bikesh Kuthu was adjudged player-of-the-match.
“The team's coordination in the first half was not good, but our players did the right moves in the second half. As a result we won the match,” said Army coach Meghraj KC.
“Three Star is one of the toughest teams so we had to fight hard for the victory. One needs to add extra effort to win the match against Three Star,” added KC.
Three Star also wasted a number of goal-scoring chances throughout the match, with Army goalie Bikesh making brilliant saves to deny Prakash Budhathoki off Nirajan Khadka's cross in the 41st minute.
Likewise, Three Star's African recruit Peter Segun's powerful shot from nearly 30 yards was not enough to beat Army goalier Bikesh.
“We lost the match despite displaying good game. Our players played well but failing to execute the chances were the setback for the team,” said Three Star coach Rajendra Tamang. “Army became successful in counter attack,” said Tamang.
Army and Three Star have played against each other in three occasions in the current season with Army winning all three matches, including
Aaha Rara Gold Cup and Simara Gold Cup, by 1-0 margin.
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