The United Auto Workers union has set an 11:59pm deadline Friday night to agree a tentative deal with General Motors, making it the 'lead' automaker in the current rounds of talks with the Detroit-based 'Big Three'.

"We are continuing to meet with the corporation and expect to put in long hours between now and the deadline," the UAW's vice-president said in an e-mail made available by an unidentified source to Reuters, which noted that, having been singled out as as the lead company GM was the potential 'target' for a strike.

"There is still much to be done and difficult issues to tackle," the vice-president reportedly said in the email. "We are fully focused on reaching a tentative agreement that meets the needs of our active and retired members."

The news agency said Ford and Chrysler had bth extended their current labour contracts with the union which were scheduled to expire today (14 September).

The current talks are to replace a four-year contract and issues such as health and retiree benefits are high on the UAW's agenda.