Top American coach Brad Gilbert has delivered a blow to British tennis after announcing that he will leave when his contract expires in September.

His decision came as Andy Murray prepared to make his first appearance at this year's Wimbledon against Fabrice Santoro on Centre Court later today.

Gilbert parted company with the British No1 last year and then agreed a short-term contract worth nearly £400,000 to continue working with the LTA on a part-time basis.

But chief executive Roger Draper confirmed today that Gilbert will return to the United States and suggested the 46-year-old only wanted to work with 'top players'.

The American is believed to have grown tired of working with British no-hopers.

He had a special brief to work closely with Alex Bogdanovic, but less than 24 hours after the British No2 lost in the first round at Wimbledon for the seventh consecutive year, Draper revealed Gilbert had had enough.

"I think Brad will move on - he wants to work with top players," said Draper. "He's also got TV commitments and so on. Brad has been great for British tennis but once he split from Andy really, it was time for Brad to go."

Gilbert headlined the LTA's initiative to bring in top-class overseas coaches when he arrived to coach Murray, Britain's juniors and high performance coaches in July 2006. Along with the likes of Paul Annacone, who had previously coached Tim Henman and Pete Sampras, Draper was keen on assembling a "top-class team in terms of credibility and quality of coaches".

Gilbert's loss is a huge blow to Draper's revolution but is not a surprise given the relative lack of progress made on the men's side, while the British women are enjoying something of a renaissance with five players inside the top 200.

Having transformed Andre Agassi and Andy Roddick from Grand Slam hopefuls into champions, Gilbert is likely to have grown frustrated by the lack of progression made by Bogdanovic in particular, who was ranked at No108 in the world last June but now languishes at No 242 following yesterday's defeat to Simone Bolelli, of Italy.

Draper will be keeping his fingers crossed that Murray progresses against journeyman Frenchman Santoro today as his own future depends on the Scots' continued success. Progress at Wimbledon for Britain's only world-class player is seen as vital if the LTA are to clinch a four-year £30million sponsorship deal for the entire sport.

Draper remains confident they can unearth a backer willing to support the sport from the very top to the grass roots, but industry experts believe the sheer breadth of the deal is causing problems.

A sponsorship expert told Standard Sport: "The LTA need Murray to have a good run at Wimbledon because they have given themselves a really difficult job. They want an awful lot of money for that four-year deal, yet there is just Murray in the top 200 of the men's game and we haven't yet found a women's player who can make a real impact.

"The major selling point for the deal is the naming rights for the Queen's tournament - now that the Artois involvement has ended - along with corporate hospitality facilities at Wimbledon. The rest of the package is very difficult to value for any potential sponsor."

With Barclays committing £20m to back the ATP end-of-year championships for the top eight men at the O2 from 2009, a major potential sponsor has been removed from the field only adding to the pressure on the LTA to clinch a deal.