NEW YORK (AFP) - World number one Novak Djokovic and five-time champion Roger Federer set up a US Open semi-final blockbuster on Thursday as the rain-ravaged event opted for a fourth successive Monday men's final. Top seed Djokovic, the runner-up in 2007 and 2010, booked his place in a fifth successive semi-final when Serbian Davis Cup-winning teammate Janko Tipsarevic retired with a left thigh injury. Djokovic, who was 7-6 (7/2), 6-7 (3/7), 6-0, 3-0 ahead at the time, will face Federer for the fourth year running after the Swiss star demolished Frenchman Jo-Wilfried Tsonga 6-4, 6-3, 6-3. The winner of that tie will play in a Monday final after besieged organisers surrendered their desperate attempts to shoehorn the remainder of the tournament, which had seen Tuesday and Wednesday washed out, into four days. The women's final will take place on Sunday instead of Saturday with both men's and women's semi-finals on Saturday. Djokovic claimed his 62nd win of 2011 when Grand Slam quarter-final debutant Tipsarevic's brave bid was undone by a thigh injury in the third set. "I sensed early in the third set when I got a break that he lost some pace on his serve and he wasn't moving as well," said Djokovic. Federer gained revenge for his landmark Wimbledon loss to the Tsonga where the Frenchman had become the first man to defeat the 16-time Grand Slam title winner from two sets to love down. It will be the fourth successive US Open semi-final meeting between Federer and Djokovic and first since the Swiss ended the Serb's 43-match winning run at the French Open in June. "I don't know if what happened in Paris will help him or me. It was a great match and a special win. It was one of the matches of the year," said Federer. "It's the biggest challenge in the sport to face him but I'm up for it and I'm playing well." Meanwhile, the U.S. Open will slide into a third week after organisers of the last grand slam of the year bowed to player pressure and agreed to change the finals schedule. US Tennis Association officials extended the tournament after leading stars such as Rafael Nadal, Andy Murray and Andy Roddick, who were all facing playing on four consecutive days to make a Sunday final, protested over the schedule. "The matches, quarter-finals, semi-finals, four rounds of a Grand Slam normally are tough matches. If you don't have rest, you have a big chance not be fit enough in the next match," said Nadal, who reached the last eight with a 7-6 (7/1), 6-1, 6-3 win over Gilles Muller, a match that was slated for Tuesday. Murray, who made the last eight with a 6-2, 6-3, 6-3 win over America's Donald Young, believes the players need more power at the Grand Slams. When asked if commercial interests -- with broadcasters ESPN holding the TV rights on weekdays and CBS leading the way at weekends -- held more sway than the players, Murray said simply: 'Yes'." Jim Curley, the US Open tournament director, said the decision to push back the final to Monday had been taken to satisfy all interests. "We revised the schedule in an effort to be fair to the players and our ticketholders," said Curley. "This is the result of a collaborative effort with the players, CBS Sports and tournament officials to address the issues that arose from the inclement weather earlier this week." Roddick, the 2003 champion, had grabbed the headlines earlier in the day when his last-16 clash against David Ferrer was suspended because of water seeping up through a crack in the surface on Louis Armstrong Stadium.