At least 10 heads of state are skipping an Arab League summit that begins Tuesday, a blow to a gathering many had hoped would tackle complex challenges facing the region such as Iraq and the Hamas-led Palestinian government.

A main reason for no-shows was the venue, Sudan. Some of the absent leaders cited security concerns, others have political differences with the Sudanese government.

The U.S. government asked friendly leaders to stay away to prevent a show of support for the Sudanese government, which is under international pressure to allow U.N. peacekeepers in Darfur, said several Arab diplomats from countries whose heads of state will not attend.

In light of the absent leaders, the annual meeting of the 22-member body was likely to be shortened to one day instead of two, Arab diplomats in Khartoum said, speaking on condition of anonymity because the decision had not been announced.

The expected absence of heavyweights such as Egyptian President Hosni Mubarak, Saudi Arabia's King Abdullah and the king of Jordan promises a lackluster summit in a year where many had hoped to see serious efforts at dealing with regional troubles.

"Rarely has an Arab summit been held with as much fogginess as the Khartoum summit — assuming it will be completed despite the increasing number of no-shows," wrote Ghassan Tueni, publisher of the leading Lebanese An-Nahar daily on Monday.

One resolution to be approved at the summit urges Arab countries to send ambassadors to Iraq, a key demand of the Iraqi government. But the low attendance could undermine the impact of such a call.

The State Department urged Arab leaders to "be as supportive as possible of the new Iraqi government" by sending ambassadors and economic assistance to Baghdad.

Sudan has sought to play down the absence of major leaders and has lined its streets with posters of the leaders and signs of welcome.

The Arab League also shrugged off the absences.

"This is not a problem," said Ahmed bin Heli, assistant secretary-general of the league. He insisted those attending represent their governments. "They act like their heads of state."

Sudan, aware of its image as an unstable country, seems to have made some efforts to prove it can provide security.

Though guards at the summit venue casually waved in people who set off metal detectors, the heads of state and ministers seemed well protected.

Leaders were taken from the airport in convoys of bulletproof cars to a neighborhood of villas where they are staying, surrounded by up to 7,000 Sudanese forces, including members of the elite Presidential Guards. Snipers were visible on rooftops and helicopters flew overhead.

But the absences were still notable for their number. Most years, only a handful of leaders stay home, often due to illness. In 2003 — just before the launch of the Iraq war — at least 11 leaders stayed away.

Egyptian officials said Mubarak was staying away after being advised by his senior security and intelligence aides not to attend.

Mubarak has not visited Sudan since a 1995 attempt on his life in Addis Ababa, Ethiopia, which senior Sudanese officials were thought to have been behind. Relations between the two countries continue to be tense.

Saudi Arabia's Abdullah was sending Crown Prince Sultan bin Abdul-Aziz in his place. Abdullah has not attended a summit since 2003, when he had a public, televised spat with Libyan leader Moammar Gadhafi, who is attending the Khartoum summit.

Jordan's King Abdullah II is also likely not to be there.

Iraqi President Jalal Talabani stayed home, apparently after being asked by political leaders to remain in Baghdad to focus on forming an Iraqi government.

Others staying away included the leaders of Comoros, Somalia, Oman, Morocco, Bahrain, and Tunisia, which has accused Sudan of hosting Tunisian Islamic activists.

Foreign ministers drew up a set of draft resolutions to be approved. One promises Arabs will continue funding the Palestinian Authority despite U.S. calls for a halt of financial aid to a government led by Hamas.