NEW YORK -- Canadians Milos Raonic and Eugenie Bouchard advanced to the second round of the U.S. Open with wins over American opponents on Monday.

Raonic moved on with a 6-4, 7-6 (8), 6-1 win over Tim Smyczek, and later, Bouchard beat Alison Riske for the fifth straight time, winning 6-4, 6-3.

In evening play, Vasek Pospisil wasn't as fortunate, falling to Austrian Andreas Haider-Maurer 4-6, 6-3, 7-6 (7), 0-6, 1-6. The Vernon, B.C., native struggled after the third set and looked to be dealing with some cramping, dropping 12 of his last 13 games en route to a first-round exit for the second year in a row.

Raonic, the 10th seed, was tested early in his match. But after emerging victorious from a lengthy second-set tiebreak, Raonic dominated the third set to advance.

Serving for the win, Raonic fired an ace clocked at 230 km/h past Smyczek to go up 40-love in the final game. Smyczek then couldn't get his racket cleanly on Raonic's serve on match point as the Thornhill, Ont., player advanced to the next round.

Despite winning in straight sets and breaking Smyczek twice in the final set, Raonic was critical of his play.

"I think sometimes I wasn't stepping up and being aggressive enough," he said. "Sometimes I was making mental lapses. I think it was that kind of stuff, those situations. I was sort of letting that stuff creep in. I wasn't as sharp as I wanted to be."

Spain's Fernando Verdasco beat Tommy Haas 3-6, 6-1, 6-7 (3), 6-3, 6-1 to set up a second-round match with Raonic. Verdasco and Raonic have split six career meetings, but Raonic has won all three matches they've had on hardcourt.

"It will be a tough match," Raonic said. "Every single time we've played it's been that way. I'm going to need to play better. But I have it within myself to find those answers and hopefully make the most of the opportunity."

Raonic is looking to advance past the fourth round of the U.S. Open for the first time in his career. He has been eliminated in the round of 16 in the past three tournaments.

Bouchard, meanwhile, is looking to salvage a disappointing season. After advancing to three Grand Slam semifinals last year, including the Wimbledon final, Bouchard has failed to live up to her early success.

The 25th seed looked solid against Riske on Monday, overcoming an early break in the first set to take control. The native of Westmount, Que., had four aces and just one double-fault while piling up 15 break point opportunities, winning five.

Riske struggled with six double faults, but did manage to break Bouchard three times.

Bouchard will face Slovenia's Polona Hercog in the second round.