American efforts to build an international coalition and capture or kill wanted terrorist Usama bin Laden suffered setbacks Sunday, as Saudi Arabia rejected unconditional U.S. military use of its airbases and bin Laden's Taliban hosts said they could not locate him. 

Reuters reported Sunday morning that while the Taliban rulers of Afghanistan had taken senior Islamic clerics' advice to ask bin Laden and his mostly Arab followers to leave the country, they said the world's most wanted man had gone missing. 

"We have still not been able to deliver the clerics' message to him because we could not find him," Abul Hai Mutmaen, spokesman for Taliban leader Mullah Mohammad Omar, told Reuters by telephone from the southern Afghan city of Kandahar. 

Asked if bin Laden was still in Afghanistan, he said: "I cannot say." 

The United States has threatened to attack Afghanistan if bin Laden, wanted for the terrorist attacks on New York and Washington Sept. 11, is not handed over for trial. 

Speaking on Fox News Sunday, White House national security adviser Condoleeza Rice was not convinced of the Taliban's inability to find bin Laden. 

"We are not going to be deterred by comments that he may be missing," Rice said. "The Taliban is going to have to begin to understand it has a very tough choice to make," she said. 

"The Taliban may be trying to find a way to get themselves out of this terrible box they're in," Secretary of State Colin Powell told NBC's Meet the Press. 

"They know where he is," said Defense Secretary Donald Rumsfeld on CBS' Face the Nation. "It is just not believable that the Taliban do not know where the network can be located and found and either turned over or expelled." 

Meanwhile, Saudi Arabia, one of America's staunchest allies in the Middle East, reportedly rejected a blanket American request to use its airbases for any offensive actions and demanded to know more about U.S. plans. 

"Saudi Arabia will not accept any infringement on its national sovereignty, but it fully backs action aimed at eradicating terrorism and its causes," an anonymous Saudi official told the Associated Press in Dubai, one of the states of the United Arab Emirates. 

The Saudis are reportedly concerned that fellow Arab states would be targets of American airstrikes, a Saudi official in Dubai told the Associated Press on condition of anonymity. 

Saudi Arabia's foreign minister, Saud al-Faisal, met with President Bush and Secretary of State Colin Powell last week. The administration was "pleased with the level of their support," one American official said Saturday. 

A senior Saudi foreign ministry official in the capital of Riyadh said that Saudi Arabia and other Persian Gulf states would provide aid only after the U.S. declares what specific groups and countries will be targeted. 

Reuters reported on Sunday, however, that the six-member Gulf Cooperation Council pledged to support anti-terrorist actions. 

"The council gave an assurance of their support and complete cooperation with international efforts to find the people who committed these terrorist acts and bring them to justice," the foreign ministers of Bahrain, Kuwait, Oman, Qatar, Saudi Arabia and the United Arab Emirates said in a joint communique. 

Washington in the past has accused the Arab states of Yemen, Sudan and Iraq of harboring terrorists, and American cruise missiles struck Sudan after the 1998 bombings of the U.S. embassies in Kenya and Tanzania, which were also seen as the work of bin Laden. 

And the Syrian and Iranian presidents have spoken by phone and agreed  that Islamic states should get together to discuss the Sept. 11 attacks, a spokesman for Syrian President Bashar al-Assad said.

Afghanistan, whose Taliban government has been harboring bin Laden and his Arab associates since 1998, is not an Arab country. American officials indicate a strike on Afghanistan could come at any time. 

Rumsfeld confirmed Sunday that an unmanned reconnaissance plane has been lost, but would not provide details on the location. He said it had been reconnoitering in advance of a possible attack. He said there was no reason to believe it had been shot down.

The Taliban has said it shot down an American unmanned plane and an aircraft of the opposition Northern Alliance.

Saudi officials have already said the United States cannot use the Prince Sultan Air Base, south of the Saudi capital Riyadh, for U.S. retaliatory attacks. Last week the commander of the U.S. Central Command's air operations, Air Force Lt. Gen. Charles Wald, shifted his operations from South Carolina to the base. 

The United States and Saudi Arabia have been close allies for more than half a century. U.S. troops have remained in the kingdom since leading the multinational coalition that ended Iraq's invasion of Kuwait in 1991 

Saudi Arabia hosts about 4,500 U.S. military personnel and an undisclosed number of warplanes at Prince Sultan Air Base. U.S. warplanes patrolling a no-fly zone over southern Iraq take off from Saudi Arabia. 

The peninsular kingdom was considering Sunday to sever its diplomatic ties with the Taliban. On Saturday, the United Arab Emirates cut off ties with the Taliban, and if the Saudis do as well, Pakistan would be the only country to recognize the Islamic theocracy as the legitimate government of Afghanistan. 

Meanwhile, the U.S. military continued to shift troops and resources to the Middle East. En route were an aircraft carrier group (two are already in the region), B-52 bombers, jet fighters and warships capable of launching ground-attack Tomahawk cruise missiles. 

The United States has "a command and control center with Saudi Arabia. It's up and running and it's operational," a senior U.S. official said Saturday. 

A U.S. military delegation drawn from the Pentagon will meet with Pakistani military officials early next week in order to coordinate possible military action against Afghanistan, a senior Bush administration official said. 

Pakistan has agreed to allow American plans to fly in its airspace in the event of an attack on Afghanistan and to seal its border in the event of such an attack. The group of U.S. and Pakistani military officials will determine the how such operations would be coordinated. 

As a gesture of goodwill, Bush lifted sanctions against Pakistan and India. The sanctions, imposed in 1998 following the nations' tests of nuclear weapons, barred economic or military aid to either country. 

Turkey, meanwhile, has agreed to allow Air Force transport aircraft to use its airspace and airports, Turkish Prime Minister Bulent Ecevit said in a letter to Bush. More than 50 U.S. and British jets are based on Turkey's Incirlik air base. 

Turkey is also willing to share intelligence on Afghanistan with the United States. 

"We appreciate all the support we are enjoying in the region and around the world," Pentagon spokesman Bryan G. Whitman said Saturday. 

Earlier this week, the Pentagon ordered the deployment of more than 100 combat and support aircraft to the area of the Persian Gulf. 

Fox News' Paul Wagenseil and the Associated Press contributed to this report