The struggling Super Aguri Formula One team said on Wednesday they were considering their future after the collapse of a planned rescue deal.
"Super Aguri F1 team confirms that it has been informed by Magma Group, the potential purchasers of the team, that its investors no longer wish to fund the intended acquisition," the Japanese team said in a statement.
"It is with deep regret that Aguri Suzuki is now forced to consider the future of the team," it added. "However negotiations with other parties continue."
It said a further statement would be issued in due course.
A team source told Reuters that there was now a real risk that Super Aguri would not be able to race in next week's Spanish Grand Prix.
Super Aguri, who barely tested pre-season due to financial constraints, have not joined others in testing at the Circuit de Catalunya this week.
With the cars and spares due to be flown to Barcelona on Saturday for the first race of the year in Europe after three long-haul rounds, the team are in a race against time.
"This could mean that we don't go to the race," said the source.
"Maybe we need a bit more backing from Honda to get us to Barcelona...Our future could be in Honda's hands now, and Bernie's I suppose," the source added, referring to Formula One commercial supremo Bernie Ecclestone.
There was no immediate comment from Magma, who had hoped to finalise the purchase by the end of last month.
The group is run by Martin Leach, a former president of Ford Europe as well as ex-chief executive of Maserati and ex-managing director of Mazda Japan.
While they have given no details of their financing plans, media reports have linked Magma to investors in Dubai.
The company's Ultramotive division are based at the same Leafield facility in central England used by Super Aguri and the now-defunct Arrows before them.
Super Aguri, whose drivers are Japan's Takuma Sato and Britain's Anthony Davidson, had hoped the takeover would secure a stable platform for the future after scraping through last season.
The team, founded by former racer Aguri Suzuki, finished ninth of the 11 teams in 2007.
(Editing by Rex Gowar)