A conference of Afghan groups trying to form a transitional government in their country has been delayed a day, with differences still dividing the rival factions, a U.N. official said Friday.

The meeting, which will take place at a hilltop hotel on the outskirts of Bonn, Germany, was scheduled to begin Monday, but will now open Tuesday, said a spokesman for the top U.N. envoy on Afghanistan, Lakhdar Brahimi.

"It was postponed by one day to give the Afghan delegations time to arrive and confer," said spokesman Ahmad Fawzi, stressing that it was a logistical delay.

Some 20 to 30 Afghans will attend, representing the four main political groups: the northern alliance, which now controls most of Afghanistan and is composed of Tajiks, Uzbeks and Hazaras; a group of Afghan exiles based in Cyprus; a Rome-based group supporting the deposed king, Mohammad Zaher Shah; and a predominantly Pashtun group of Afghans based in Peshawar, Pakistan.

The Taliban will not be represented at the meeting at the Petersberg Hotel overlooking the former West German capital, but there will be representatives from the Pashtuns, the dominant ethnic group in Afghanistan.

Fawzi said he expected the meeting to last one or two weeks, but added: "We will be there as long as the parties are talking."

Playing down expectations of an agreement in Germany, he said more meetings might be needed to get the Afghans to agree on an interim government.

"This is the first step on a long road to establishing good governance in Afghanistan," Fawzi said.

As U.N. officials prepared for the conference, northern alliance forces advanced on the Taliban's last stronghold in northern Afghanistan, the city of Kunduz, amid discussions of a Taliban surrender. The Taliban are still clinging to Kandahar in the south.

To fill the political vacuum, Fawzi said, the conference will seek to forge an agreement on a provisional council that would run a post-Taliban Afghanistan until a broad-based, multiethnic government is set up.

The spokesman, however, wouldn't predict swift success in ending 22 years of strife — including a 10-year Soviet occupation and a subsequent civil war — that has divided and devastated the central Asian nation.

"We can't be totally confident that we are going to get an agreement," Fawzi said. "I think it's quite an achievement that we are getting the parties together at this stage."

Bringing peace to Afghanistan is a major challenge for the United Nations.

"I think the United Nations will be viewed for the next 10 years on how it does in Afghanistan," U.N. spokesman Fred Eckhard said.