Roger Federer says becoming the oldest world number one in tennis history – 14 years after he first topped the rankings – is a “dream come true”.

The 36-year-old beat Robin Haase 4-6 6-1 6-1 in the last eight of the Rotterdam Open to replace Rafael Nadal, 31, at the top of the standings.

Federer surpassed eight-time Grand Slam winner Andre Agassi, who was 33 when he was deposed in September 2003.

“This one means the most at 36 years of age, almost 37,” the Swiss said.

“When you’re older you have to work double the amount. You have to wrestle it back from someone who’s worked hard to get there.

“Reaching number one is the ultimate achievement in tennis. It’s been an amazing journey and to clinch it here, where I got my first wildcard in 1998, means so much.”

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Federer’s hopes of reaching the semi-finals in the Netherlands looked slim when he lost the first set, but he dropped just two further games to set up a tie with Italian Andreas Seppi or Russia’s Daniil Medvedev.

At the end of the match, the 20-time Grand Slam champion sat down and wiped away tears, before returning to the court to take the acclaim from the crowd and receive a trophy for his achievement.

He first became world number one in February 2004, but has not topped the rankings since October 2012 and slipped to a low of 17th in January 2017.

That was after he spent six months out recovering from an operation on a knee problem.

However, he has since won eight titles, including Wimbledon last year and two Australian Opens.

Analysis – more to come?

Six-time Grand Slam winner Stefan Edberg on BBC Radio 5 live

The way Federer plays, the way he moves on the court, he is probably the only one who was going to get to number one at this stage, this late in his career.

I doubt there is going to be somebody in the near future doing the same. He has done an extraordinary job. It is quite incredible, I don’t think he believes it himself, and I think everybody is surprised.

He can play freely now, because whatever he does now is going to be a bonus. Hopefully he can keep the momentum going, and if he keeps being healthy he is got a really good shot at Wimbledon again.

Federer in numbers

• When the ATP rankings are updated on Monday, it will be five years and 106 days since he was last at the top – the longest gap between stints.
• He first reached the summit 14 years and 17 days ago in February 2004 – the longest gap between first and most recent spells.
• The Swiss is only 13 behind Jimmy Connors’ record of 109 tour-level titles

World number one Caroline Wozniacki reached the Qatar Open semi-finals, but Simona Halep withdrew because of injury after winning her quarter-final.

Dane Wozniacki, the Australian Open champion, beat Germany’s Angelique Kerber 7-6 (7-4) 1-6 6-3.

World number two Halep beat American CiCi Bellis 6-0 6-4, but then revealed she had a right foot injury.

“It’s going to be dangerous if I force it,” said the Romanian, who is out until at least Indian Wells in March.

“I am surprised that I could play three matches and to win them. I felt pain every day.”

Halep said it is the same injury that affected her run to the Australian Open final in January.

“The MRI shows that I have fluid and also tendinitis at the fourth toe, so I have just to take care of it and think about my health first,” added the 26-year-old.

Halep’s withdrawal means fourth seed Garbine Muguruza, who beat Caroline Garcia 3-6 6-1 6-4, will go straight through to Sunday’s final.

Czech Petra Kvitova reached the semi-finals after Germany’s Julia Gorges retired from their quarter-final while trailing 6-4 2-1.

By reaching the semi-finals, Wozniacki became just the fourth woman in history to pass $30m (£21m) in prize money.

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American Ryan Harrison will not face action over a claim he directed a “racial slur” at compatriot Donald Young during the New York Open.

The chair umpire intervened during the pair’s first-round meeting on Monday after they argued at a change of ends.

After the match, Young, 28, tweeted: “I’m shocked and disappointed to hear you tell me how you really feel about me as a black tennis player.”

The ATP said on Friday that it could find no evidence of any wrongdoing.

“The match footage did not pick up verbal exchanges between the players,” said the ATP, which also reviewed interviews with match officials and other tournament staff.

“At this time no evidence has been found to support the allegation that Ryan Harrison used a racial slur during the match.”

Harrison, who won the match 6-3 7-6 (7-4), responded to Young’s tweet by saying any video or audio from the match would “100% clear me”.

The 25-year-old added: “The accusations are absolutely untrue. I’m extremely disappointed that someone would say this in reaction to a lost tennis match.”

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World number one Caroline Wozniacki has complained about Monica Niculescu’s “disturbing” grunting after beating her in the third round at the Qatar Open.

The Australian Open champion won 7-5 6-1 but accused the Romanian of making too much noise and spoke to the umpire.

Wozniacki, 27, continued her criticism off-court, calling Niculescu “a player that tries to get into your head”.

The WTA has said umpires can act on grunting if it is deemed to affect an opponent through a ‘deliberate act’.

“I just tried to let him [the umpire] know to pay attention to her grunting because she’ll hit the ball and two seconds later when the ball is on my side and I’m right about to hit, she’ll start grunting and make a noise, and she’ll change the grunt according to what she feels like,” Wozniacki claimed.

“It’s disturbing. It’s in the rules that they’re not supposed to do that so I was just making sure the umpire was paying attention to that. And she stopped doing that after.”

Wozniacki moved back to the top of the women’s rankings after winning her first grand slam title in Melbourne in January.

But Niculescu, who beat Maria Sharapova in the first round in Qatar, has defended her game.

She told Romanian TV channel Digi Sport: “That was very bad from her, I have never heard a number one talk like that. I am really disappointed by what she said and I think she gives herself too much importance. I didn’t want to get in her head. This is how I play.”

Roger Federer said he “never imagined” he would be world number one again as he moved to within one victory of being the oldest man to achieve that feat.

The Swiss 20-time Grand Slam champion beat Germany’s Philipp Kohlschreiber 7-6 (10-8) 7-5 to reach the quarter-finals of the Rotterdam Open.

If Federer, 36, beats Robin Haase in their last-eight tie on Friday, he will replace Rafael Nadal at the summit.

“I’ve struggled to try and get there. I had to win a lot of matches,” he said.

Federer, who became world number one for the first time in February 2004, has not topped the rankings since October 2012 and slipped to a low of 17th in January 2017.

That was after he spent six months out recovering from an operation on a knee problem.

However, he has since won eight titles, including Wimbledon last year and two Australian Opens.

The oldest number one previously was eight-time Grand Slam winner Andre Agassi, who was 33 when he last topped the rankings in September 2003.

Federer had to work hard against Kohlschreiber to maintain his hopes, though, prevailing in a 54-minute first set after a lengthy tie-break.

The second set was no less attritional, with Federer breaking for the only time in the contest to go 6-5 ahead before serving out to clinch a quarter-final place on his second match point.

“Tonight was complicated, I had to fight and struggle,” he said. “I had a good gameplan going in, but I was never able to completely pull it off.”