Sixth seed Petra Kvitova handily defeated Irina-Camelia Begu 6-3 6-2 in first-round action at the U.S. Open on Monday but the Czech admitted it took some time getting used to playing in front of the empty stands at Flushing Meadows.

The twice Wimbledon champion converted four of five break point opportunities and fired 23 winners to defeat her Romanian opponent.

"I had to motivate myself from the beginning to the end," the 30-year-old said in an on-court interview.

She also lamented the lack of crowd support at the event, which is being played without any fans in attendance due to the Covid-19 pandemic that has claimed over 180,000 lives in the United States.

"It's really mentally tough, to be honest," she added.

She added that being in the bubble meant she was no longer free to do what she would have wanted during her off days at the hardcourt major.

"Going out for the coffee, sitting in Central Park. Suddenly this is not (an) option," Kvitova told reporters.

Facing off on Court 17, the pair enjoyed unseasonably cool weather under cloudy skies, which was a welcome change from previous years when soaring temperatures left players drenched in sweat.

World number 12 Kvitova put the pressure on early, winning 10 of 12 net points and launching two aces in the first set.

Kvitova, who suffered a second-round exit last year at Flushing Meadows, will next face either Kateryna Kozlova of Ukraine or American Whitney Osuigwe.