Wimbledon champion Rafael Nadal ensured he will take the world number one spot after reaching the semi-finals of the Cincinnati Masters on Friday.
Nadal's 7-6 6-1 win over Nicolas Lapentti means the Spaniard will end Roger Federer's four-and-a-half-year reign on 18 August at the latest.
Nadal, who now plays Novak Djokovic, could even usurp Federer immediately if he wins in Cincinnati.
"It's emotional. Getting to be number one is so satisfying," said Nadal.
Federer's run of 235 consecutive weeks at the top of the ATP rankings was put in jeopardy when he was knocked out of the tournament on Thursday by 16th seed Ivo Karlovic.
Nadal has been right behind him in second place since 25 July 2005, a span of 158 straight weeks.
And with two more wins this weekend, the 22-year-old would trade places with the Swiss, who he beat in last month's epic Wimbledon final as well as in the French Open final in June.
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Nadal added: "I am happy because I have been fighting a lot these last three years, although I was happy as number two as I won a lot of tournaments.
"But for sure, number one is a goal and I am very happy."
Nadal's win over Ecuador's Lapentti was his 32nd straight victory, taking him a step closer to a sixth successive tournament triumph.
Should Nadal lose Sunday's final he would top the rankings on 11 August, while a semi-final defeat would delay his coronation for another week.
But he admitted he will need to change up a gear if he wants to progress past third seed Djokovic.
"If I want to beat Djokovic I have to play better than in this match (against Lapentti) and my best match in Cincinnati for sure.
"But the important thing is that I continue to play well and continue to win."
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