Silverstone is in danger of losing its place on the MotoGP schedule, with a draft of the 2018 calendar listing the host venue for the British Grand Prix as TBA.
The Northamptonshire track has hosted Britain's MotoGP round since 2010 after the event moved away from long-time home of Donington Park, which held the race from 1987 to 2009.
Silverstone made a deal with the Circuit of Wales to continue hosting the event after the proposed Ebbw Vale-based facility signed a five-year deal with series promoter Dorna covering 2015-'19.
That agreement has effectively been nullified by CoW's inability to secure the government guarantees it needed to be able to commence construction, leaving Silverstone's future in the balance.
Dorna is understood to be in negotiations with both Silverstone and Donington for 2018 and beyond - a situation reflected by the venue for the British round being listed as 'TBC' on a draft calendar issued on Wednesday.
Aside from the British Grand Prix's TBC status, Thailand's Buriram Circuit is the only new addition on the draft schedule.
It has been given a provisional date of October 7, two weeks before the start of a triple-header comprising the Motegi, Phillip Island and Sepang rounds.
As previously reported by Autosport, the 2018 season will start a week earlier than this year, with the Qatar season-opener set to take place on March 18.
The Barcelona date has been pushed back a week to June 17, with the subsequent Assen and Sachsenring rounds also taking place later than in 2017 - shortening the summer break to three weeks.
Thailand's arrival also means the season will conclude one week later, on November 18, in Valencia.
Provisional MotoGP 2018 calendar
March 18 Qatar
April 8 Termas de Rio Hondo
April 22 Austin
May 6 Jerez
May 20 Le Mans
June 3 Mugello
June 17 Barcelona
July 1 Assen
July 15 Sachsenring
August 5 Brno
August 12 Red Bull Ring
August 26 TBA
September 9 Misano
September 23 Aragon
October 7 Buriram
October 21 Motegi
October 28 Phillip Island
November 4 Sepang
November 18 Valencia