LONDON (AP) _ Angolan rebel leader Jonas Savimbi said Tuesday his U.S.-backed UNITA movement and the Angolan government will sign accords this week that should end their 15-year civil war by the end of May.

United Nations troops will be deployed in the African nation 15 to 20 days after the cease-fire to monitor the transition to Angola's first democratic elections in the autumn of 1992, Savimbi said.

The May cease-fire agreement will be signed by the Angolans and by the United States, the Soviet Union and Portugal, the former colonial power in Angola, Savimbi said. The three nations are supervising peace talks that began April 4 in the Portuguese resort of Estoril.

''There is no more a problem between us and the MPLA,'' Savimbi said at a news conference.

MPLA are the Portuguese initials for the Popular Movement for the Liberation of Angola, the ruling Angolan party. Savimbi's group is the National Union for the Total Independence of Angola.

''The MPLA and UNITA have realized that after 15 years of war there is an impasse. No one can achieve a military victory on the ground. We all realize we have to go through a political solution,'' Savimbi said.

The agreement could end of one of Africa's longest wars, which began in 1975 after Portugal granted independence to Angola following a guerrilla war. The war has devastated the country and pitted South Africa and the United States against the Soviet Union and Cuba.

Savimbi, apparently seeking to preempt an official announcement later in the week, spelled out details of the reported accord at the start in London of a five-nation European tour.

He said the accord would be signed at the latest on Thursday. The only delay was the late return to Estoril of one of the Portuguese negotiators, he said.

Savimbi said that ''to create a climate of understanding'' fighting will be suspended a week before the official cease fire is signed in Portugal on May 29 or May 30.

''Fifteen to 20 days after that signing then the cease fire will be officially imposed which means that the United Nations will deploy their forces to supervise the cease fire,'' said Savimbi.

He said UNITA would then become a political party, opening offices in the Angolan capital, Luanda.

Savimbi gave no details of how many U.N. troops would be deployed or from which countries. But he said U.N. troops would monitor the Angolan navy and air force during the transition.

All the concerned parties will prepare elections and monitor the establishment of single army, said Savimbi. The new army, between 20,000 and 40,000 strong, would be drawn equally from UNITA rebels and government troops, he said.

The 50,000 Cuban troops deployed in Angola at one point have mostly departed and are due to be out completely by the end of June.