By NBF News

Woods takes a break during one of his practice rounds at Pebble Beach

Tiger Woods and Phil Mickelson will battle it out for the world number one spot at the US Open, which starts at Pebble Beach on Thursday (1500 BST).

Woods, a 14-time major winner, has led the rankings since 2005 but will lose that honour if Mickelson wins at the iconic California course.

In-form Lee Westwood leads the British challenge and is paired with Woods and Ernie Els for the opening two rounds.

Lucas Glover, the 2009 winner, is paired with Open champion Stewart Cink.

The US Open returns to a lengthened Pebble Beach course for the first time since 2000, when Woods stormed to a record 15-stroke victory.

Since then he has won 11 majors, including two more US Opens, but the 34-year-old comes into this year's tournament on the back of a tumultuous seven months.

Woods abandoned golf at the end of last year following numerous revelations about his private life and has only played four tournaments since his return to the sport.

He tied for fourth at his Masters comeback in April while he missed the cut at the Quail Hollow Championship in May and withdrew during The Players Championship the following week with a neck injury.

“I only had a few weeks to get ready for Augusta after being off for quite a while. Now I've been playing tournament golf basically since April,” he said.

“I'm starting to find out how much I can and can't push myself each and every day as far as practice.

“It's great to be back. The more I play, the more I get my feel back.”

World number two Mickelson, who won the Masters this year for the third time, has an incredible record of five runner-up spots at the US Open, including famously double-bogeying the last in 2006 when he only needed a par for victory.

A second-place finish on his own would be enough for Mickelson to move to the top of the world rankings if Woods finishes outside the top four.

Glover was one of the surprise major winners in 2009

Should Woods make the cut but finish outside the top 18, Mickelson would need to finish no worse than third on his own, and if Woods misses the cut, his fellow American would need to finish no worse than a two-way tie for third to lead the rankings.

“It's a special tournament for me,” said Mickelson, who turned 40 on Wednesday. “Having come so close, this is a tournament I'd very much like to win.

“I still have a sense of pride in the way I've played, but I would like to win my national Open. Winning this tournament would be something that would help define my career.”

Westwood, the world number three, has had a fine run in recent majors, finishing in the top three of the last three tournaments.

He finished third in the US Open at Torrey Pines in 2008 and comes into this year's tournament with victory in the St Jude Classic last week.

“The main challenge is fulfilling my own expectations,” he said. “I've been putting myself in a position to win a major and feel like I ought to be expected to win one now.”

The last Briton to win the US Open was Tony Jacklin in 1970 but with four Englishmen in the world's top 10, Ian Poulter believes that drought is due to come to an end.

“If you're a betting man, your chances now are better than ever before,” said the English world number eight.

Last year, unheralded American Glover secured a rain-hit US Open at Bethpage by two shots from Mickelson, David Duval and Ricky Barnes.

Pebble Beach has hosted just four US Opens and has seen a host of changes since Woods's victory 10 years ago.

It has been lengthened by 194 yards and toughened up with new greens, changes to 11 bunkers and the reshaping of fairways and rough.

And South African Els, winner of the US Open in 1994 and 1997, is not expecting anyone to emulate Woods's 15-shot victory.

“The greens are going to be very tricky,” he said. There's a huge difference from the morning to late afternoon… when you hit the brown patches the ball really doesn't stop on the green. But it's a great golf course.

“Tiger, he was out of this world that week. If the weather is half-decent, I think someone can shoot under par. And if we have very bad weather, over par will win.”