The United Auto Workers union has put General Motors on notice: We want a contract deal by 11:59 pm Sunday. If an agreement isn't reached, UAW members could go on strike.

The union and General Motors are continuing to talk in their attempt to negotiate a new four-year pact.

General Motors (GM) said Saturday it had received the union's notice and was "working with them to address the issues." GM said it would "remain committed to obtaining an agreement that is good for employees and the business."

A strike would be the first in the auto industry since 2007.

Any deal between GM and the UAW will probably follow the outlines of one reached with Fiat Chrysler on October 7

A big sticking point with Fiat Chrysler was the pay gap between recent hires and veteran employees. The new Fiat Chrysler deal narrows this gap and guarantees recent hires $28 an hour after seven years. UAW members at Fiat Chrysler (FCAM) approved that contract on Thursday.

About 11,000 of General Motors' 52,600 UAW-member workers are in the lower-paid tier.

The UAW agreed to the two-tier system nearly a decade ago when American automakers were suffering deep financial problems. Chrysler and GM both ended up in bankruptcy court in 2009.

Today, GM in particular is enjoying much better times. The company this week announced a record quarter for profits. GM's financial success adds pressure on UAW leaders to strike a good deal or face the risk that any proposed contract will be rejected by rank-and-file members.