General Motors president Dan Ammann has flown to Britain to hold crisis talks with the Government and unions over fears that thousands of jobs at Vauxhall could be axed as part of a takeover.
Mr Ammann is understood to be meeting Business Secretary Greg Clark and Unite general secretary Len McCluskey at Westminster following news that Peugeot owner PSA Group is in talks to acquire GM's loss-making European operation.
The deal would include Vauxhall, which has plants at Ellesmere Port and Luton employing 4,500 staff.
Mr Clark is also seeking a meeting with PSA Group at the earliest opportunity to discuss the proposed deal that would see Vauxhall and Opel shift to the French government-backed automotive giant.
This would see GM exit the UK and Europe, while transforming PSA Group into Europe's second-largest car maker with a 16% share of the market.
Vauxhall is a major employer in the UK, with around 35,000 staff, including 23,000 in its retail network, 300 at a customer contact centre in Luton and 7,000 in its supply chain alongside workers at its two factories.
Germany has already expressed concerns at the proposed takeover, with Chancellor Angela Merkel's cabinet discussing on Wednesday what impact the tie-up would have on the 19,000 German jobs at Opel.
It came on the day GM chief executive Mary Barra is said to have flown to Germany to visit Opel's headquarters in Ruesselsheim to discuss the deal.
Mr McCluskey has called on the Government to extend the assurances offered to Nissan over Brexit to the rest of the UK car industry to help secure jobs at Vauxhall.
Following a meeting with Mr Clark on Wednesday, Mr McCluskey said Unite had stressed to the Government that it ''will not accept any job losses or plant closures as a result of this move''.
He said Vauxhall's UK plants must be offered the same level of certainty over their future as Nissan, adding: ''It does seem as if Brexit is a factor in this decision as GM does rely heavily on its links throughout the EU supply chain."
Nissan announced in October that it was investing in production of new Qashqai and X-Trail models at Sunderland after receiving Government assurances that EU withdrawal would not affect the plant's competitiveness.
PSA Group, which owns the Citroen and DS brands, formed an alliance with GM in 2012 in an attempt to make production more efficient by combining purchasing power and larger scale.
The US motor giant behind Chevrolet and Cadillac said last year that it had to raise UK car prices by 2.5% after the plunge in the value of the pound following the EU referendum result caused the British car industry to hit a ''speed bump''.
Announcing its full-year results last week, the Detroit-based firm said GM Europe had narrowed losses to 257 million US dollars (£206 million) in the year to the end of December, from a loss of 813 million US dollars (£651 million) the year before.