Sixth seed Murray, enjoying the highest grand slam seeding of his career, needed four sets to overcome tricky left-hander Llodra, France's world number 38, but was thrilled to have come through the test 6-4 1-6 7-5 7-6 (9-7) at the Billie Jean King National Tennis Centre in New York.

"It was always going to be tough," Murray said. "He's got a huge serve and being a lefty makes it tougher.

"He's won doubles slams before – two tournaments at the start of this year.

"He will give anyone a tough match – very rarely will he lose easily. He moves really well up at the net, doesn't give you a lot of rhythm."

Murray, who next faces world number 48 Jurgen Melzer of Austria, claimed the combination of Llodra's chip-and-charge tactics and his big serve made the Frenchman doubly difficult to break down.

"I don't mind playing against guys that come to the net a lot, but he serves so well. That's what makes it tough," he said.

"When you find it hard to break someone and they're coming in all the time against you, then it makes it tricky.

"But I started to return well toward the end of the third set – obviously broke him twice in the fourth. That was the difference compared with the first three sets, even though I won the set.

"Apart from the game where I broke him, I won very few points on his serve. Same again in the second set, so it was really tricky.

"He's a really tough guy to play against and I was happy I won in four sets."

Ends