Rep. John B. Anderson, whose campaign for the presidential nomination has begun to run out of steam, said yesterday an independent candidate could win the White House this year but said he still hasn't made up his mind about running as one.

"I won't make a decision for two or three weeks," he told reporters yesterday in Los Angeles, where he had spent several days vacationing with his wife, Keke.

"I said I was coming out here to sit under a eucalyptus," he said. "But I ended up on the beach, with not a tree in sight. There was not sufficient shade to bring my cerebrations to a conclusion."

Anderson has been under pressure for several weeks to decide about an independent bid. He has yet to win a primary this year and was particularly disappointed last week when he finished third behind Ronald Reagan and George Bush in Wisconsin, a state he had once hoped to win.

In the last week, his campaign has shown signs of weakening. Most troublesome is fund raising. The response to his direct mail solicitations had been excellent, but campaign sources said yesterday that contributions have begun to slacken.

If Anderson were to run as an independent, he would be denied $29.4 million in federal funds available to the major party candidates and would have to raise all the money himself.

Anderson described himself yesterday as genuinely undecided about an independent candidacy. "Fundamentally, I'd like to give people in this country a broader and better choice than they'd have with Carter and Reagan," he said.

"Don't put me down in your book as just another George Wallace who's out to send a message," he said. "There is an unusually high level of dissatisfaction with the Reagan-Carter choice. I think you could win as an independent candidate."

He cited a recent Gallup Poll showing that 21 percent of those surveyed said they would support Anderson as an independent candidate as evidence of "unprecedented" support at this stage of the campaign.

Anderson's campaign staff remains divided over the issue, with more pressure for an independent candidacy coming from outsiders.

Anderson's wife, an influential adviser, has been researching the question of an independent candidacy and has been reported as favoring it. But she said last week she has strong reservations about launching such a candidacy and went to California with divided opinions.

She particularly fears that the press would write off an independent candidacy as a frivolous exercise and believes that would hurt Anderson and such a candidacy.