A buoyant Lech Walesa predicted Saturday that authorities will legalize Solidarity next month and that the union will play a key role in helping the government solve Poland's economic problems.

"I'm convinced Poland needs understanding and first of all agreement. We are committed to agreement. We must seek agreement to get the situation under control," the Solidarity leader said at a news conference.Solidarity officials and top government leaders on Friday set a Feb. 6 date for long-awaited, broad-based talks on the future of the banned union and reforms to combat Poland's economic and political crisis.

Walesa said Solidarity's aim is to deal with the government, not usurp it. "I said it in 1981 and I repeat it now. We don't want to take over power. We can't. It would be fatal. But we have a deal to make with this government."

He also said the talks, known as "the round table," could help open the way for other groups that, like Solidarity, do not have Communist Party approval, to participate in trade union, economic and political activities.

"Today, I'm thinking about our chances, and when I see we are breaking the monopoly, I'm convinced we have great chances," Walesa said.

The talks appear to be part of a government attempt to bring the opposition into the battle against Poland's economic decline, which has led to chronic shortages, a massive foreign debt and an apathetic populace.

The government first proposed the talks in August during a wave of strikes that marked Poland's worst labor unrest since Solidarity was crushed in the martial law crackdown of 1981.

The government banned Solidarity in October 1982, and Walesa refused to agree to talks until it reinstated the trade union.

In a dramatic reversal of policy last week, the Communist Party Central Committee offered to legalize Solidarity if the union agreed to obey the law and, among other conditions, stop accepting financial aid from the West.

Last Sunday, Solidarity's leaderhship agreed to negotiations on the offer.

Walesa said the talks should be kept as short as possible.

"As far as the round table goes, we have said many times and repeat it, we want to make it as fast as possible. The tentative time is six weeks," he said. "But there are terribly difficult and complicated problems and they can't be solved that quickly."

Walesa said he envisioned Solidarity becoming a strong trade union with good relations with the government.