NEW YORK (Reuters) - Andy Murray dropped a set for the first time at this year's U.S. Open on Friday but recovered quickly to ease his way into the third round.

The defending champion beat Argentina's Leonardo Mayer 7-5 6-1 3-6 6-1 in two hours and 41 minutes on a steaming hot day at Louis Armstrong Stadium.

It was clear the Scotsman was in for tough workout when he needed almost an hour to clinch the first set but he seemed to back in control when he raced through the second.

Mayer broke Murray's serve at the start of the second set and calmly held all of his own service games to push the match into a fourth set but the third seed regained control and ran away with it.

"It was a very tough match," said Murray, whose next opponent is Germany's Florian Mayer. "Both of us did a lot of running.

"I started to move better as the match went on. He's a big hitter of the ball and I had to defend a lot."

(Reporting by Will Swanton; editing by Julian Linden)