LIBREVILLE, Gabon (AP) _ Zairian President Mobutu Sese Seko postponed plans to return to his country from a summit, adding to the speculation that he will go into exile rather than confront rebels advancing on his capital.

Despite repeated assurances by his aides that Mobutu would return to Kinshasa, Zaire, on Friday, his plane remained on the tarmac of Libreville's airport and diplomatic sources said he would stay there at least until later today.

The 66-year-old dictator, dying of prostate cancer and losing a seven-month civil war, has agreed to long-delayed elections and acknowledged he is too ill to be a candidate.

Mobutu directed the military earlier in the week to prepare the country for elections. He made no mention of resigning or giving power to a transitional authority or to rebel leader Laurent Kabila, as demanded by the rebel force that now controls nearly three-fourths of Zaire.

In eastern and central Zaire, where the civil war has displaced Rwandan Hutu refugees who had been living there since 1994, the United Nations stepped up efforts to bring them back home to Rwanda.

U.N. officials said they were doubling the number of refugees to 4,000 that they move each day from camps in the Zaire's central jungle.

The world body announced its decision Friday in Geneva, Switzerland, amid pressure from Zairian rebels and the Rwandan government. Rebels have told the United Nations it wants all 80,000 refugees in the region out of the country by the end of June. So far about 15,000 have been sent home.

The Rwandan Hutus fled their country fearing retaliation for a Hutu-led massacre of half a million people, mostly ethnic Tutsis. Most of the refugees have returned to Rwanda, where Tutsis now are in power. Remaining refugees have reported being attacked by the rebels, many of them also ethnic Tutsis.

Seeking a peaceful solution for Zaire, South African Deputy President Thabo Mbeki met Friday with Kabila in the southern Zairian city of Lubumbashi. Mbeki said the rebel leader had agreed to meet Mobutu next Wednesday aboard a South African ship for a second round of peace talks in Pointe Noir, Congo.

Mbeki arrived later Friday in Libreville, saying he would propose the date to Mobutu. ``He's got to be at the meeting,'' Mbeki said.

Rebel foreign minister Bizima Karaha in Lubumbashi said Friday that Kabila was only going to meet Mobutu to secure his resignation. He added that a proposal for Mobutu to turn power over to a transitional figure was unacceptable.

In Kinshasa, Zaire's capital, pressure was increasing on Mobutu to cede power. For the first time, political parties within the parliament announced their support for Kabila.

But Mobuto also had some support as several hundred demonstrators gathered in front of the U.S. Embassy to call for his return.

Rebel forces have been meeting uncommon resistance since Sunday in their drive on the capital. Fighting was reported to be especially heavy around Kenge, 120 miles to the east. The rebels say former Rwandan Hutu soldiers and troops from Jonas Savimbi's National Union for the Total Independence of Angola, or UNITA, from Angola made up the bulk of troops fighting on the government side.

In a sign of the rebels' increasing hold on the country, a Canadian mining company said Friday it will make a $50 million down payment to Zairian rebels to develop what may be the world's largest copper and cobalt deposits near Lubumbashi.

The Vancouver-based Tenke Mining Corp. contract, with a total value of $250 million, would be the largest single infusion of cash for the rebels since they began their drive in September.

As the rebels press toward the capital, investors have flocked to their headquarters to discuss mining plans for the mineral-rich country.

While Mobutu has insisted he will return to Zaire, Western diplomats and at least one Mobutu aide have said privately they believe the president might use his trip to Gabon as a stepping stone to exile in a third country.

The Washington Post reported Friday that Zairian Prime Minister Gen. Likulia Bolongo appears to be preparing to flee the country with $7 million in government funds.

The paper said the apparent theft of the funds was disclosed in a cable from the U.S. Embassy in Zaire to the State Department. Government sources in Washington confirmed existence of the cable.

``Circumstances point to the possibility that Prime Minister Likulia has prepared for a speedy departure from Kinshasa with a couple of large suitcases of cash,'' the cable says.