NEW YORK: World number ones Serena Williams and Novak Djokovic will launch their bids for the US Open title on Monday's first day of competition, tournament organizers announced Friday.

In a Twitter posting, the tournament said top halves of brackets on both the men's and women's draws would play matches on the first day of competition.

That means three-time defending champion Williams, trying to complete the first calendar-year Grand Slam since Steffi Graf in 1988, will meet Russia's Vitalia Diatchenko on day one, likely in a feature match on Arthur Ashe Stadium and quite possibly in the night session opener.

Williams, coming off her fourth consecutive major title last month at Wimbledon, seeks her 22nd career Grand Slam singles title, which would match Graf for the all-time Open Era record and move her two shy of Margaret Court's all-time record of 24.

Djokovic, seeking his second US Open crown, will face Brazil's Joao Souza in his opener on Monday while his possible quarter-final opponent, Spanish star Rafael Nadal, begins Monday against Croatia's Borna Coric.

The other top half quarter of the men's bracket will see Japanese fourth seed Kei Nishikori, last year's US Open runner-up, face France's Benoit Paire in his first match while defending US Open men's champion Marin Cilic, a ninth seed from Croatia, opens against Argentina's Guido Pella.

The tricky quarter-bracket with Williams also features her older sister Venus, a seven-time Grand Slam champion, meeting Puerto Rico's Monica Puig in round one.

Russia's Maria Sharapova, who has 18 losses in 20 meetings with Serena Williams but could face her again in the US Open semi-finals, launches her title bid against Australia Daria Gavrilova.

No exact times have been announced for any matches on Monday.

In past years, the US Open schedule has seen the men play the first round over three days and set up a “Super Saturday” with the men's semi-finals and women's final.

But that scheduling was scrapped in favor of making sure the men and women each have an off day ahead of the championship match, which did not happen in the “Super Saturday” format.

Among the interesting openers that will not be played Monday are Swiss second seed Roger Federer against Argentina's Leonardo Mayer, British third seed Andy Murray against Aussie bad boy Nick Kyrgios and Swiss fifth seed Stan Wawrinka against Spaniard Albert Ramos-Vinolas.

Kyrgios sparked outrage after comments to Wawrinka during a match about his girlfriend having possibly been unfaithful.