Svitolina, Federer battle thru'

Ukraine's fourth-seeded Elina Svitolina, fighting to become world number one, and Austrian sixth seed Dominic Thiem captured rain-interrupted matches Wednesday to reach the second round of the US Open.

Svitolina, seeking her sixth title of the year and first Grand Slam crown, held off 42nd-ranked Czech Katerina Siniakova 6-0, 6-7 (5/7), 6-3 while Thiem finished off Australian Alex de Minaur 6-4, 6-1, 6-1 under sunny skies.

There were 87 matches scheduled Wednesday in the year's final Grand Slam event after rain washed out most of Tuesday's agenda, 11 of them halted first-round affairs.

Former world number one Maria Sharapova was set to face Hungary's 59th-ranked Timea Babos in a later second-round match at Arthur Ashe Stadium.

Svitolina, who dropped six of nine tie-breaker points when her match resumed, survived a third set, breaking for a 4-2 edge and serving out for the victory.

"It was a little bit unlucky to stop because I was playing good," Svitolina said. "Today was a little bit of a mess in my head. It was tough to keep my focus. I'm happy I could win the third set and play really good tennis.

"I was just trying to fight for every ball. You can't win if you're not mentally strong."

Thiem, a semi-finalist at the past two French Opens, was working to adapt his skill on the Paris red clay to maximum impact on the New York hardcourts.

"I'm pretty pleased with the performance," Thiem said.

"I'm trying to improve my hardcourt game. I cannot play my clay game here. I can't stay close to the baseline."

Canadian 18-year-old Denis Shapovalov, who faces French eighth seed Jo-Wilfried Tsonga later, can become the youngest man in the third round of a Grand Slam since Australia's Bernard Tomic at the 2011 Australian Open and in the US Open since American Donald Young in 2007.

Earlier on Tuesday, Roger Federer made a narrow escape in a tense five-set thriller, sorting out worries about a back injury and poor preparation to reach the second round.

The 19-time Grand Slam champion outlasted 70th-ranked US 19-year-old Frances Tiafoe 4-6, 6-2, 6-1, 1-6, 6-4 in a shockingly tough battle that boosted his hopes of a deep run on the New York hardcourts.

"I think this is going to give me a lot of confidence," Federer said. "It's important to go through all of these emotional roller coasters early. That pressure is not fun but it's what you have to go through."

The match was Federer's first since losing the Montreal final to Alexander Zverev nearly three weeks ago. He withdrew from Cincinnati with a sore back the following week.

"I was worried in the beginning from my back issue from a couple weeks ago but I loosened up," Federer said, calling his back "extremely well" and adding "it's only going to get better from here."