The British Grand Prix looks unlikely to go ahead in July after the British government announced it will not give sports such as Formula One an exemption from new quarantine rules as a result of the coronavirus pandemic.
Anyone arriving in Britain from June 8 will have to enter a 14-day period of self-isolation, home secretary Priti Patel confirmed on Friday.
The list of exemptions, which included medical professionals and freight workers, was not extended to top-level sports.
F1 and Silverstone had already agreed a provisional plan to host two races at the circuit over two different July weekends. In that plan, the Silverstone races were set to follow a back-to-back slate of events at Austria's Red Bull Ring on July 5 and 12.
F1 had hoped to be granted an exemption and earlier this week hinted at the economic damage which could be caused to the championship if one was not granted.
However, a Formula One spokesman said discussions with the government are ongoing: "We have been working closely with government on the implications of the policy for Formula One and Silverstone.
"Those discussions are ongoing at this time with the aim of finding a solution with safety as our first priority."
Silverstone manager Stuart Pringle told Sky Sports he was hopeful of a solution: "I am very clear that the importance of the industry is understood by government, so I remain optimistic that a sensible and pragmatic solution, which puts the onus on the sport quite rightly to come up with the right solution, can be found."
A statement released earlier this week said: "A 14-day quarantine would make it impossible to have a British Grand Prix this year. Additionally, it has a major impact on literally tens of thousands of jobs linked to F1 and supply chains."
F1 is believed to be in talks with Hockenheim, the most recent host circuit of the German Grand Prix, until its contract ran out in 2019, about filling the gap in the new season schedule originally reserved for Silverstone.
Pringle said Silverstone can be flexible on dates, but whether a championship can be held is still unknown: "We can accommodate later dates in August if required, possibly even into September conceptually, but it's not so much about what we can accommodate...it's can the championship piece together a calendar that allows them to go from country to country?
"And can they have the confidence to commit to that in a timescale that allows the freighting plan to come together because it's the logistics that are the key to getting this championship underway."
Information from Reuters was included in this report.