George McGovern, newest of seven announced candidates for the Democratic presidential race, said tonight that the government should provide home buyers a one-time mortgage at a rate of less than 10 percent.

If elected, the former South Dakota senator said, he would try to "restore the American dream of home ownership" by offering the government-guaranteed mortgage loan.

Speaking at a presidential candidates' forum at Cornell University, McGovern said a goal of his administration would be to put the unemployed back to work through public works programs similar to those initiated by President Franklin D. Roosevelt.

"People condemn Franklin Roosevelt and the New Deal for their deficits, but on the whole it was brilliant as it helped to provide more job opportunities," he said. "The private sector cannot do it all alone."

McGovern also said that U.S. Marines should be withdrawn from Lebanon and that U.S. military involvement in Central America should be halted.

"Now that we have achieved a cease-fire in Lebanon, we should take our Marines out. It would be difficult to withdraw under fire, but we now have a chance to do it under the cease-fire," he said.

McGovern said the United States could cut $20 billion to $25 billion from its budget simply by getting rid of military waste.

He also called for the dismissal of Interior Secretary James G. Watt, saying Watt's "antics have diverted the attention from his destruction of the public's domain."

McGovern, who was defeated by Richard M. Nixon in the 1972 presidential election and lost his South Dakota Senate seat in 1980 during President Reagan's landslide victory, spoke at the last of seven forums sponsored by the New York State Democratic Committee.

An estimated 800 listeners jammed the floor, hallways and exits of the auditorium, which has a capacity of 550.

"He speaks like a human being," said Craig Mack, 32. "It's not like it's show business with him. He's genuine, and he obviously knows what he's talking about."

Debbie Van Ryn, 25, a graduate student, said she came to the forum questioning McGovern's reasons for wanting to run again in 1984. She said she left believing he has no chance against front-runners Walter F. Mondale and Sen. John Glenn (D-Ohio).

"I don't think he'll get nominated, as much as I would like him to," she said.

Glenn had appeared at a similar forum Monday in Syracuse, and Mondale was at a session in Rochester Wednesday. New York Gov. Mario M. Cuomo (D) and Sen. Daniel Patrick Moynihan (D-N.Y.) were on hand for Glenn's appearance, but neither showed up for McGovern's speech and question-and-answer session.