The Grand Slam tournament, which begins in New York on Aug. 27, will also have a strict seven-minute period from when players enter a court until action starts after the warm-up.

Both the serve clocks and strict timing for the warm-up were tested during qualifying matches at Flushing Meadows in 2017.

"We would like to keep the pace of play moving," U.S. Tennis Association spokesman Chris Widmaier said in a telephone interview Wednesday, confirming the main-draw changes that were first reported by The New York Times. "That's our goal."

One other element that the USTA tried out during qualifying matches at last year's tournament that will not make it into the main draw this year is allowing coaches to communicate with their players during matches.

"We certainly will not see coaching in the main draw this year," Widmaier said.

The amount of time taken between points by players has been a topic of conversation in tennis for quite a while now. And although chair umpires are supposed to monitor the seconds, it has not been done uniformly, in part because there is not a readout available for players and spectators to see.

Now there will be something akin to a basketball shot clock for US Open matches.

If a player's 25-second allotment before serving lapses, the chair umpire will issue a warning. The player can be docked a point after a second violation, and then a game after a third, Widmaier said.

Before the start of play, the clocks in New York will mark a seven-minute limit split up this way: one minute from when players step on court until the coin toss; five minutes for the warm-up; one minute until the opening point. Delays can result in fines of up to $20,000, according to Widmaier.