Former MG Rover workers could take direct action to prevent the company's new Chinese owner shipping Longbridge equipment to the Far East.
A union source issued the warning as Nanjing Automotive met officials from the Transport and General Workers' Union, who again raised concerns about its long term plans.
The T&G suggested Nanjing should join forces with the Shanghai Automotive Industry Corporation, which it beat in the bidding for the Birmingham car maker.
A Nanjing spokesman described the talks as " constructive" and said they focused mainly on the company's new strategic partnership with Fraser Welford-Winton, former head of the Powertrain engine making division.
However, there was continuing concern that the company is aiming to carry out a "lift and shift" exercise at the plant and a union source said such a move would be resisted.
"The meeting was positive and Nanjing did listen to our concerns, but we have made it very clear to them that we are not going to sit back and cooperate with a lift and shift," said the source.
"A lot of people have not secured jobs since Rover collapsed and if there is nothing left at Longbridge then the future for many people is bleak."
A business source close to the bidding process also claimed that Nanjing did not have the financial muscle to ensure car making remained at Longbridge.
The source expressed concerns that Nanjing would need a partner with a larger global presence if it was to successfully produce cars in Birmingham with Mr Welford-Winton's firm, the GB Sports Car Company.
Nanjing stated its intentions to create up to 2,000 jobs in the UK after it bought MG Rover from administrators.
However, the business source said: "A lot of people were very surprised when the administrators agreed to the deal with Nanjing.
"Nanjing have made a lot of losses recently so where is the money for the on-going business going to come from?"
Tony Woodley, general secretary of TGWU said yesterday's talks were " positive". The unions have consistently backed the SAIC bid, claiming that it would lead to more jobs and a more stable future for the MG Rover workers.
A spokesman from Nanjing said: "We had a very friendly and constructive meeting.
"The unions told us they understood our position and look forward to more dialogue with us."
The agreement made between Nanjing and Mr Welford-Winton last week could see MGs rolling off the production line in the next 12 months and a new MG roadster, possibly a revival of the MG Midget, in the next two years. It would also see between 1,000 and 2,000 jobs being created.