DETROIT (AP) _ Strike plans remained on hold today at two General Motors Corp. parts plants in Michigan and Wisconsin as the automaker and the United Auto Workers union resumed talks over local contract issues.

There was some optimism after negotiators worked long hours through the weekend in separate talks to resolve the disputes and an eight-week strike at a Pontiac, Mich., pickup truck assembly plant.

``There was progress made at all the locations,'' spokesman Reg McGhee said at UAW headquarters. ``Bargaining was pretty intense all weekend.''

Talks resumed this morning to resolve the dispute at GM's Delphi Energy & Engine Management Systems plant in the Milwaukee suburb of Oak Creek, Wis. McGhee said the UAW was extending its Thursday strike deadline on an hourly basis.

The plant makes catalytic converters used in most GM cars and trucks built in North America and in some overseas. Assembly plants would have to close within days if the Oak Creek plant were idled.

Health and safety, subcontracting and job security were the key issues at the plant, which has 870 UAW-represented workers.

At a metal stamping plant in Grand Rapids, Mich., the union continued to extend its Friday strike deadline hour by hour. Talks continued through the weekend and resumed today, said spokeswoman Mary Urby of the GM Metal Fabricating Division.

The plant employs 2,340 UAW-represented workers, who make body panels for a variety of GM cars and trucks, including the redesigned '97 Pontiac Grand Prix and Oldsmobile Intrigue.

There were some signs that the strike threats were putting pressure on negotiators to reach agreement to end the strike at GM's Pontiac East pickup plant near Detroit.

``We're encouraged that the bargaining is picking up,'' GM Truck Group spokesman Dan Flores said. ``We're encouraged by the length of the meetings.''

Negotiators met for nine hours Saturday and more than 14 hours Sunday. Talks resumed this morning.

The UAW represents 5,900 workers at the plant. It wants more workers hired to reduce overtime and job stress. GM has resisted adding more permanent jobs. The plant is due to be retooled in the coming year to produce a new generation of pickups that require fewer workers to assemble.

Sources close to the talks, speaking on condition of anonymity, said there has been some progress, but that the key staffing issue was still unresolved.

The strike is the fifth one against the automaker so far this year.

A tentative contract was reached Friday at a GM foundry in Saginaw, Mich., averting another threatened strike. A ratification vote was scheduled Wednesday for the plant's 912 UAW-represented workers. Details of the agreement were not released.

The local contracts expired in September. Several other GM plants remain without local contracts, months after the UAW and GM approved a three-year national contract.