By Alan Baldwin
SILVERSTONE, England (Reuters) - Silverstone's owners triggered a break clause in the British Grand Prix contract on Tuesday that throws the country's Formula One race into doubt after 2019 unless a new deal is agreed.
This year's race, the halfway point in the season, takes place on Sunday with a big Formula One promotional event planned in London on Wednesday.
"This decision has been taken because it is not financially viable for us to deliver the British Grand Prix under the terms of our current contract," British Racing Drivers' Club (BRDC) chairman John Grant told a news conference at the track.
"We sustained losses of 2.8 million pounds ($3.60 million) in 2015 and 4.8 million in 2016, and we expect to lose a similar amount this year."
Grant said Silverstone, which has the biggest turnout of any race on the calendar, was the only circuit in Britain that could host the race and hoped a more sustainable deal could be reached over the next three years.
A spokesman for Formula One, owned by U.S.-based Liberty Media, said the decision and the timing of the BRDC's announcement was regrettable.
"The week leading up to the British Grand Prix, should be a week of great celebration for F1 and Silverstone," the spokesman said.
"We deeply regret that Silverstone has chosen instead to use this week to posture and position themselves and invoke a break clause that will take effect in three years time.
"Our focus is still to preserve the British Grand Prix. We will carry on negotiating with the promoter in good faith and in private to reach a fair and equitable solution."
Silverstone hosted the first world championship grand prix in 1950 and Britain, home to seven of the 10 teams as well as triple world champion Lewis Hamilton, has been on the calendar every year since.
Sean Bratches, the sport's new commercial managing director, last week described Silverstone as "one of the jewels in the crown of Grand Prix racing" and Liberty have said repeatedly that they want to safeguard the sport's historic venues.
Grant said the BRDC remained fully supportive of the changes Liberty are bringing to the sport but the non-profit members club could "no longer let our passion for the sport rule our heads".
The promoter's fee for hosting the race increases by five percent annually, which means it has grown from 11.5 million pounds in 2010 to 16.2 million this year. By 2026, it would have risen to 25 million.
The BRDC said it had reached a tipping point and revenue from ticket sales and hospitality was not enough to cover the cost.
(Editing by Hugh Lawson and Ed Osmond)