esotho's acting prime minister, Chief Peete Peete, said in an interview tonight that he feared South Africa might be preparing to launch a reprisal attack on his country on the false assumption that insurgents from there had exploded a car bomb in the South African city of Bloemfontein yesterday.

Speaking by telephone from Maseru, Peete also complained that South Africa was causing economic dislocation in Lesotho by obstructing the flow of traffic between the two countries.

A spokesman for the South African defense force would not respond to Peete's allegations. The only South African reaction was a police spokesman's denial that the border delays were deliberate. Brigadier Francois Steenkamp, new chief of the South African security police, said vehicles crossing the border were being thoroughly searched because of increased terrorism in South Africa and because Lesotho had complained of rebels crossing into its territory.

Peete's fears stem from reports by a Bloemfontein newspaper, the Friend, and the South African Broadcasting Corp. that they received telephone calls today from a representative of the African National Congress in Lesotho claiming responsibility for the bombing.

"It is quite improbable that these calls could have been genuine," Peete said. "South Africa launched an attack here last December, claiming it was against ANC bases. Can you believe that if the ANC had planted this bomb they would have been so foolish as to indicate where they had operated from?

"The whole thing is obviously a hoax, a bluff," Peete said. "My fear is that it has been done either by the South Africans or by someone else who is against the Lesotho government, to set us up as a target for a reprisal attack."

Asked why South Africa should want to do this, Peete replied: "For no other reason than to please the South African public. There must be retribution somewhere for these bombs, and we are number two to Maputo."

This was a reference to a South African air raid on the Mozambique capital of Maputo Monday. South Africa claimed to have hit ANC insurgent camps there following a car bomb explosion that caused heavy civilian casualties in Pretoria May 20.

The Pretoria and Bloemfontein bombings and South Africa's reprisal raid represent a major escalation in the long-simmering racial conflict here.

Keith L. Brown, the U.S. ambassador in Maseru, said on the telephone tonight he thought the main problem in the Lesotho capital lay with the slow traffic across the border.

"It has been going on since Tuesday night and is beginning to cause serious concern here," Brown said.

A Maseru businessman interviewed on the telephone said the traffic holdup extended several miles either side of the border and a number of cargo vehicles had been delayed more than a day.

Some containing refrigerated produce had returned to their depots in South Africa, and people in Maseru were starting to get anxious about possible shortages.