By Larry Fine

NEW YORK (Reuters) - Frenchman Gael Monfils overwhelmed worn-out compatriot Lucas Pouille 6-4 6-3 6-3 to become the first man into the semi-finals of the U.S. Open on Tuesday.

Tenth seed Monfils was his dynamic self and invincible from the service line in a commanding win over 22-year-old Pouille, who was coming off three successive five-set wins including a fourth-round upset of 14-times grand slam winner Rafa Nadal.

Monfils finished 24th seed Pouille with his 13th ace to lead off a huge day for the French, who placed three men in the quarter-finals of a grand slam for the first time since the 1947 French Open.

"I'm happy with my performance. I think it is never easy to play quarter-final against a French guy, you know," Monfils told reporters after the two-hour match. "I think I handled it pretty good mentally and tennistically."

Monfils did not face a single break point in his demolition of Pouille, winning a daunting 85 percent of points on his first serve as he unleashed deliveries that topped out at 135 mph and registered 34 outright winners.

"Of course I was a bit tired today," said Pouille, who also ousted 15th seed Roberto Bautista Agut of Spain along the way. "I played four matches, one in four sets, and then all three in five.

"I did my best today. Gael was playing very good. He's physically very fit. He's moving so well. I think he was better than me today."

The red-hot Monfils maintained an impeccable run to the last four with his fifth consecutive straight-sets win in a hard court season in which he won the ATP World Tour 500 event in Washington, reached the semi-finals in Toronto and the quarter-finals at the Rio Olympics.

Monfils, who reached his second career grand slam semi-final and first since 2008 in Roland Garros, will meet either top seed Novak Djokovic or ninth-seeded Jo-Wilfried Tsonga, the third Frenchman in the last eight at Flushing Meadows.

Against Djokovic, Monfils is still looking for his first victory after a dozen defeats. He has won three of seven meetings with good friend Tsonga.

Monfils, 30, said he regards Djokovic as one of the greatest players ever, but would not shrink from a chance to play the Serb for a berth in Sunday's U.S. Open final.

"He's a better player than me, definitely. I think I have no shame to say it. He is better than me," said Monfils, before suggesting that a breakthrough was possible on any given day.

"You can be the best, but one match is enough, you know. If I face him, I will take the one match as enough."

(Editing by Frank Pingue)