Federer claimed his 50th win of 2014 as the 17-time major winner, playing in his 60th successive Grand Slam and bidding to become the oldest major winner in over 40 years, defeated Australia's Marinko Matosevic 6-3, 6-4, 7-6 (7/4) to register his 23rd win in 24 night matches in New York yesterday.
"It was a bit more difficult than I thought it was going to be in the third set. Marinko has a big game," said second seeded Federer who hit 10 aces and 41 winners and was cheered on by basketball legend Michael Jordan.
Women's world number one Williams, the double defending champion who is also seeking a sixth title, was equally untroubled, defeating 18-year-old compatriot Taylor Townsend, 6-3, 6-1 in just 55 minutes.
Williams, like Federer, a 17-time major winner, has failed to make it past the fourth round at the Australian Open, French Open and Wimbledon this year.
Also Read
"This was the first Slam I ever won. I love coming out to play -- I never want it to stop," said Williams, who was dressed in a leopard-print dress for the occasion and next tackles compatriot Vania King.
But on Tuesday Bellis, ranked at a lowly 1,208 and aged just 15, knocked out Australian Open runner-up, Dominika Cibulkova, the 12th seed, 6-1, 4-6, 6-4 to become the youngest player to win a match at the US Open since Anna Kournikova in 1996.
"I went into the match thinking it was going to be such a great experience, but I never thought I would come out on top winning," said Bellis who, as an amateur, had to pass up the $60,000 prize money to avoid jeopardising a college sports career.