A Sudanese government spokesman said on Saturday that United Nations peacekeepers now would be welcome in Darfur after a peace agreement between Khartoum and one of the rebel groups.

Bakri Mulah, secretary-general for external affairs in the Information Ministry, issued the invitation on behalf of the Khartoum government after the agreement was reached Friday in Abuja, Nigeria.

The Sudanese government initially rejected calls for U.N. peacekeepers to replace the thousands of African Union peacekeepers now in Darfur.

CountryWatch: Sudan

"We heard the appeal of the U.N. secretary general (for U.N. peacekeepers to joint those of the African Union)... . Now there is no problem," he said.

Two rebel groups, though, have rejected the accord backed by the African Union, United States, Britain, the European Union and the Arab League and skipped the signing ceremony in a hall at a Nigerian presidential villa Friday night.

Optimism was muted by that and a history of failure to live up to agreements struck over two years of negotiations in the Nigerian capital.

At the U.N., American Ambassador John Bolton welcomed the agreement but said U.N. peacekeepers would become essential if the agreement were to hold.

"Recognizing that this is a very positive development in Abuja, we now would like the government in Khartoum to follow through and give the necessary visas and other arrangements to allow the U.N. planners to go in," Bolton said. That would lead to the strengthening of the African Union force during the transition, he said.

Deputy Secretary of State Robert Zoellick, who helped spur negotiators to agree to stop the killing, said the embattled East African region was far from safe even if the peace agreement were to take hold.

U.S. President George W. Bush intervened during the difficult negotiations, sending a letter to the largest rebel group, Minni Minnawi, with assurances that the United States would give strong support to implementation of the peace accord, help monitoring compliance, hold accountable those who do not cooperate and support a donors' conference for Darfur, Zoellick said in a telephone interview from Abuja with reporters in Washington.

In Cairo, Arab League Secretary-General Amr Moussa welcomed the agreement and urged the rebel groups that opted out to reverse their decisions.

Moussa, in a statement faxed to The Associated Press, expressed confidence that the agreement would end the violence and open the way for reconstruction and development.

Khartoum had dropped opposition to a U.N. peacekeeping force, citing new conditions created by the peace deal.

"There would be no problem to have the support of the United Nations and other partners, the U.S. and EU, to help in implementation," Mullah told AP.

Mulah said the agreement also would help in repairing relations between Sudan and Chad, strained over the flood of refugees from Darfur.

Beyond that, he told AP, he expected Minnawi, the head of the Sudan Liberation Movement, to play an important role in the peace process as a member the Sudan's national unity government.

Mulah said the agreement was not closed to other rebel groups who had refused to sign.

"The other parties still have a chance to do so, but if they refuse then they will be treated just like the Janjajweed (the anti-rebel militia the government was accused of backing) or any other outlaw factions.

"This is not a government stand, it is that of the international community, the AU, the U.N. and the U.S. They will not tolerate any violation of the agreement, " he warned.