On a dramatic day, it all came down to two shots - Lahiri missing a three-foot putt on the 18th and home boy Sangmoon Bae's messing his third shot on 18th, which rolled back onto the fairway.
Lahiri's miss came after Chris Kirk holed a massive 15-foot pressure putt to give the American a full point instead of a half.
Bae, who goes in for Military Service after the event, also had a chance to snatch a half point, but it ended with a botched-up chip. Bill Haas, one of the picks made by his father and captain, Jay Haas, held his nerve and won the last point and with it the Presidents Cup.
"I have to give credit to Chris as well. The team played great. Obviously I'm disappointed with my week. Hopefully I get a chance to redeem myself in years to come."
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He added, "I was pretty sure what the line was and I made a good stroke. But I think I did what I've done all week: Misread putts."
Despite the loss, captain Nick Price said he was happy and proud of his International team.
"Anirban and to Moon (Bae), you know, they were in very difficult predicaments today, which I don't think they have ever felt before.
"But it's all part of the experience. Today is a day they will never forget, but I hope that they use it in a positive way to take the next step."
Lahiri also mentioned, "I had Bubba Watson come up to me about a minute after we finished up and he said that he had done the same exact thing. Both of us thought -- I guess. I don't know about his putt. I didn't see it. It looked like right in to me. That's why I hit it. Went left to right and caught a big part of the lip. Spat it out.