After a year of closed-door meetings with tennis players seeking a greater say in the sport and a larger slice of Grand Slam revenues, the U.S. Open is making big changes.

New York's Grand Slam tournament will increase its annual prize money to $50 million by 2017 -- roughly double what it was last year -- and permanently schedule the men's semifinals on Friday and men's final on Sunday starting in 2015.

As part of an unprecedented five-year agreement with the men's and women's professional tours, the U.S. Open also is making an additional $4.1 million increase to this year's prize pool, on top of an already-record $4 million jump announced in December. That brings the 2013 total payout to $33.6 million from the $25.5 million in 2012.

The U.S. Tennis Association announced the changes Wednesday, a day after they were formally presented to the ATP Player Council at a meeting in Key Biscayne, Fla. Details were described to the AP on Tuesday by USTA officials.

"Roger Federer said it perhaps best of all: It's time for us to work together, as opposed to working against each other," USTA Executive Director and Chief Operating Officer Gordon Smith said in a telephone interview.

Federer, the 17-time major champion, is president of the ATP Player Council. He is not playing in the tournament that begins this week at Key Biscayne, but participated in Tuesday's meeting via telephone. Federer joined other top players, including current No. 1 Novak Djokovic, in lobbying the USTA and organizers of other major tournaments in an effort that began at the tournament in Indian Wells, Calif., about 12 months ago.

"It's a very positive step for players. You know, it proves that players, I think, are more united than ever. I believe that these are some significant changes in the negotiations with Grand Slams," Djokovic said Wednesday in Key Biscayne. "It hasn't happened for, I think, ever or for many, many years that we have such increases. We just feel like we deserve it. There is a lot of players -- not just the top players, but a lot of players who are in top 100, top 200 -- who deserve to have a better living from this sport."

Aside from wanting more money, some male players complained the U.S. Open had been the sport's only Grand Slam tournament with their semifinals and final on consecutive days. The USTA liked its old "Super Saturday" setup -- two men's semifinals and the women's final all on that day's schedule at Flushing Meadows, followed by the men's final Sunday -- but tournament director David Brewer acknowledged it was time to scrap it.

"We realize the game has changed and how they play the game is different even than it was 10 years ago," Brewer said. "The format we've had for 30 years was putting players and the tournament in jeopardy at some point."

In December, the USTA said it would move the 2013 women's singles final to Sunday and the men's final to Monday, building in a day of rest ahead of each title match and moving from a 14-day tournament to 15 days.

That schedule will remain in place in 2014, but the U.S. Open will shift things in 2015: women's semifinals Thursday, men's semifinals Friday, women's final Saturday, men's final Sunday.

"Personally, I am not happy with a Monday final, but it is the way it is for next two years," Djokovic said. "I think we have to accept it, and then after that, it all goes back to normal, hopefully, for Sunday final, like every Grand Slam has."

Another change coming in 2015: Men's first-round matches will be played over the U.S. Open's opening two days, instead of three.

Asked to describe the nature of the negotiations with players, which began about a year ago, USTA Chairman of the Board and President David Haggerty said: "I wouldn't say necessarily `pressure.' I would say `spirited discussions."

The USTA does not plan to pay for the higher prize money with a similar leap in ticket prices.

"Frankly, we'll take somewhat of a hit," Smith said, "but it's the right thing to do for the Open and for the players, so we're doing it."

The distribution of the new prize money -- how much will go to the singles champions, for example, or to losers in the early rounds or to doubles teams -- hasn't been decided. An announcement is expected closer to the start of the U.S. Open, which runs from Aug. 26 to Sept. 9.

The USTA did confirm its commitment to equal paychecks for men and women. But it is not ready to say exactly how prize money will go up between now and 2017, other than that it will increase each year.

"We have a good idea, but we are still working on that," Smith said. "We've shared our thinking (with the ATP), and I think we're all pretty much on the same page, but we're working out the details."

The USTA's prize money announcement comes before the French Open (which starts May 26) and Wimbledon ( starts June 24) say how much they will offer this year.

Haggerty said the sport's leading tournaments have not coordinated their efforts to placate players.

"This agreement ... really allows us to focus our energies ... on growing tennis and participation. This allows us to know generally what the future looks like," Haggerty said.

"Each of the Grand Slams make their own decisions. ... We have not had conversations with the other Grand Slams to tell them what we're doing," he added. "They will hear about it when it is announced."