The Scot, who had not played since Wimbledon, said he had tried everything to be fit for the final grand slam of the year, which starts on Monday.
“I tried obviously resting, rehabbing to try and get myself ready here,” an emotional Murray told a news conference at Flushing Meadows.
“I was actually practising OK the last few days but it's too sore for me to win the tournament, and ultimately that's what I was here to try and do.”
The three-times grand slam winner, who won the U.S. Open in 2012, has been struggling with the injury for much of the summer.
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He was suffering during his French Open semi-final defeat by Stan Wawrinka in June and had to pull out of two exhibition matches in the run-up to Wimbledon.
It was clearly a big problem during his home grand slam tournament, when he bowed out, clearly in pain, in the quarter-finals, to Sam Querrey.
Murray withdrew from the Rogers Cup in Montreal and then the Western and Southern Open this month in the hope of giving his injury more time ahead of the U.S. Open.
The 30-year-old hinted that he may have to follow the example of Novak Djokovic and Stan Wawrinka in taking off the rest of the year to allow the injury to heal fully.
“I’ll definitely make a decision on that in the next few days,” Murray said.
“That's something that I'll sit down and decide with my team. But I'll decide on that in the next couple of days, for sure.”
Murray held the number-one world ranking for 41 weeks before being overtaken by Rafa Nadal last week.
“I want to be back on court as soon as I can,” he said.
“If it means that ... I can play before the end of the year, then that's what I would love to do. I miss competing, and I'll try to get myself back on court as soon as I can.
“But obviously I'll need to make the correct decision and really think it through these next couple of days with my team, and then make that decision.”
Murray began the year as the world number one, having hit top spot for the first time after a stunning end to last year, when he won five straight tournaments, including the ATP World Tour Finals.
Should Murray decide not to play for the rest of the year, his ranking is likely to slide to around 16th.
(Reporting by Simon Cambers, editing by Ed Osmond, Neville Dalton)
