MONTREAL: Andy Murray made sure of claiming the world number two ranking, but he'll have to get past Juan Martin Del Potro on Sunday to claim the ATP Montreal Masters crown.

Third-seeded Murray beat French seventh seed Jo-Wilfried Tsonga 6-4, 7-6 (10/8) in the semi-finals and is set to rise to second in the world for the first time in his career.

Sixth-seeded Del Potro, who won the title in Washington over Andy Roddick last weekend, continued his dominance over the three-time Wimbledon runner-up as he beat the fifth-seeded American 4-6, 6-2, 7-5.

Del Potro fired 19 aces in a semi-final victory lasting just over two hours.

"I'm so happy to be in another final," said the Argentinian. "It's a great sensation. Andy and I are both very strong on serve. I just played better than him in the important moments."

Del Potro owns former number one Roddick after winning all three of their meetings. He trails Murray, 3-1, earning his lone victory in their last meeting at the Madrid Masters in May.

Scotland's Murray will replace Rafael Nadal in the slot behind Roger Federer when the new rankings are released on Monday.

"It's great, in terms of rankings it's the biggest step that I've made so far," said the 22-year-old, who is bidding for a fifth title of the season.

"I played consistently well this year, so bar winning a Slam, I've done enough to justify being number two and getting closer to hopefully one day becoming number one - it's one of my goals.

"I've put in a lot of hard work to get to this stage, and I keep working hard to go one step farther."

Murray's trip to the final insured his promotion after Nadal - back after a break of more than two months nursing tendinits in his knees - lost in the quarter-finals on Friday to Del Potro.

The change makes Murray the first player other than Nadal or Federer to rank number two since July 18, 2005, when Australia's Lleyton Hewitt stood second behind Federer.

"This is very special for me," said Murray. "Roger and Rafa have been one and two for the past five years. I played well and I'll try to justify this new ranking, but it will be very difficult.

"For five years it's been Rafa and Roger on one and two, they are I think the two best maybe of all time. So it's pretty special to get in between them."

Murray reinforced his status as the highest-ranked British player since the rankings began in 1973 as he won his 49th match of the season.

"It's always tough against him, because he dominates or he dictates what happens in the match because of the way that he plays," Murray said of 2008 Australian Open finalist Tsonga.

"I just had to stay solid and make enough balls for him to make a few mistakes and me to come up with a few big returns."

Murray recovered from an early break to win the opening set. In the second-set tiebreaker he trailed 4-2, and saved two Tsonga set-points before claiming the victory on his second match point.

"Andy's a very good player and it's tough to go to the net every time against him," said Tsonga. "But that's fine, I'm OK with that."