The emergency agreement between Ford Motor Co. and the United Auto Workers could be the basis for a new contract between General Motors Co. and the union, GM President James McDonald said yesterday.

GM is waiting to hear whether the UAW will agree to reopen the current GM contract as it did in Ford's case. The union and GM broke off negotiations on Jan. 28 because too many local union officials opposed the labor cost concessions GM was seeking.

Ford, however, reached a new 2 1/2-year agreement with the union that trades a nine-month wage freeze and other reductions in labor costs for a guaranteed-income plan for senior workers, profit sharing and other job security measures.

The UAW's national GM bargaining committee has voted unanimously to reopen early negotiations with GM, Knight-Ridder reported yesterday.

Union members said yesterday that earlier opposition in committee ranks to reopening contract talks has disappeared in the wake of heavy layoffs and recently announced plans to close seven GM plants, according to the news service.

The Ford plan, ratified last week by its UAW members, will not produce the labor costs savings that GM was looking for in its initial bargaining with the auto workers, but McDonald said yesterday that the Ford plan is now a fact of life for GM.

He told a National Press Club audience that GM doesn't know what the UAW will propose if it agrees to reopen bargaining, but if they ask for the Ford plan, "We'd be hard put to say no."

In an interview later, McDonald said GM would not accept the Ford terms without negotiations. GM's position on job security could be different than Ford's, but the Ford agreement "could become the basis for the negotiations," he said.

UAW President Douglas Fraser said Tuesday that it will take several more days to assess the views of GM's 340,000 union workers about reopening the negotiations.

GM initially sought reductions in holidays, fringe benefits and other labor costs large enough to lower GM car prices by up to $1,000 a car. Although the UAW rejected the amount, it agreed with GM that any savings would be subtracted from car prices, dollar for dollar.

McDonald said that deal died when negotiations broke down and won't be offered again by GM.

He acknowledged that the company's relative financial strength compared with Ford and Chrysler Corp. has made it harder to negotiate labor cost reductions.

The most recent auto sales data showed the industry's contining woes. GM's sales in the Feb. 21-28 period plunged 35.3 percent from their level a year ago, while Ford was down 10 1/2 percent and Chrysler fell 8.2 percent. American Motors Corp. was off 44.6 percent, and Volkswagen of America reported a 44.3 percent sales decline.

The decline is exaggerated somewhat by the comparison with the 1981 figures because the industry was enjoying a brief sales spurt then, brought on by rebates. Although the companies have been forced to sweeten rebate programs continuously, they no longer are having a dramatic impact on sales.

The five major U.S. auto companies delivered 456,942 cars in February, 15.9 percent below the February 1981 total based on daily selling rates and the worst performance for that month in 20 years.