In a surprise move, the United States has begun airlifting hundreds of members of an Iraqi exile group into southern Iraq, vanguard elements of what a high-ranking Pentagon officer said would form the basis of a new Iraqi army.

Taking up camp on the outskirts of Nasiriyah, the soldiers belong to the Iraqi National Congress and are being led by Ahmed Chalabi, a London-based former banker and principal founder of the INC. Chalabi was among those flown to the southern Iraqi city from Kurdish-controlled northern Iraq.

The lightly armed force is prepared to perform a variety of missions, from delivering humanitarian aid to hunting down supporters of Iraqi President Saddam Hussein, INC spokesmen said. But U.S. Marine Gen. Peter Pace, vice chairman of the Joint Chiefs of Staff, suggested the group's significance may be as much political as military. "These are Iraqi citizens who want to fight for a free Iraq, who will become basically the core of the new Iraqi army once Iraq is free," he said on ABC's "This Week."

A senior Pentagon official said the decision to send the force had been made within the last few days and reflected a desire to enlist more native Iraqis in "working the cities," where most U.S. forces have at best received a tepid welcome from the local population. Some of the force will be deployed to other southern cities, the official said, while another group will assist U.S. forces in northern Iraq. A large number of those sent south are Shiites who had been Iraqi soldiers and had taken refuge in the north over the past decade, the official said.

The group's sudden move to southern Iraq, and the role played by the Pentagon in facilitating it, is likely to prompt controversy, fanning suspicions that senior U.S. defense officials are trying to give Chalabi a favored place in the formation of a new Iraqi government. The INC is one of six anti-Hussein organizations -- including groups representing northern Iraqi Kurds and southern Iraqi Shiites -- that have formed an uneasy coalition under U.S. auspices.

Chalabi, 58, is a polarizing figure in Washington and among Iraqi exiles. His supporters, centered in the Pentagon and Vice President Cheney's office, credit him with vision and formidable political skills that helped Bush administration hawks press their case for toppling Hussein. But to others, particularly in the State Department and CIA, Chalabi is an unreliable partner with only a limited base of support in Iraq after 45 years spent living outside the country.

The insertion of INC forces is likely to boost Chalabi's hopes of becoming the leading expatriate voice -- and perhaps the strongest Iraqi voice -- in a postwar "interim authority" envisioned by the administration, although senior U.S. officials have insisted they are not trying to elevate one figure over another. Chalabi has pressed U.S. officials to create a free Iraqi military force that could challenge Hussein, a notion that U.S. analysts inside and outside government have considered politically unwise and militarily doomed.

The airlift began Friday with U.S. military aircraft ferrying Chalabi and the INC soldiers from northern Iraq to Tallil airfield in southern Iraq. By today, the number is due to reach 700, according to Zaab Sethna, an INC spokesman with the group. An INC news release on the deployment said the contingent has been designated the 1st Battalion of Free Iraqi Forces.

Sethna said the group is working with a U.S. Special Forces unit and living in tents and buildings on the edge of Nasiriyah, a city 175 miles southeast of Baghdad that was the scene of fierce fighting between U.S. Marines and Iraqi forces a week ago. In one of their first actions, Sethna said, members of the group met yesterday with several "tribal leaders" in the area.

"The tribal leaders were happy to see Iraqis serving with U.S. troops," Sethna said by satellite phone.

Asked what missions the INC force expected to undertake, Sethna mentioned distributing humanitarian supplies, protecting U.S. military supply lines, maintaining law and order, and rooting out paramilitary fighters from Saddam's Fedayeen and the Baath Party.

"We'll go wherever Gen. Franks orders us to go," he said, referring to Gen. Tommy R. Franks, head of U.S. Central Command, which is running the war.

The INC group's unexpected arrival in southern Iraq followed a Pentagon announcement last week that a program based in Hungary to train Iraqi expatriates as guides, translators and security officers had been suspended. Fewer than 100 candidates completed the course, defense officials said, despite a goal of at least 1,000.

Explaining the reasons for the suspension, Defense Secretary Donald H. Rumsfeld and Gen. Richard B. Myers, chairman of the Joint Chiefs of Staff, told a news conference that the onset of war had overtaken the program. Neither official mentioned the formation of an INC battalion or its imminent arrival in southern Iraq.

"This is a different concept," Sethna said. "Those who were trained in Hungary have been sent as individuals to military units to serve various liaison functions. We weren't part of that program. Many of us had volunteered to go to Hungary but didn't. We're a separate cohesive group." He said creation of the battalion had been "discussed at length" within the U.S. government and planning had been in the works for about two months. About half the soldiers, he said, come from inside Iraq.

"Some have military training, and others do not," said Riva Levinson, an INC consultant in Washington. "But they have a familiarity with Iraqi society and can be a bridge between coalition forces and the civilian population."

Just what role the INC will play in a post-Hussein Iraq has been a subject of considerable debate within the Bush administration. The interim authority is envisioned as a bridge to a new democratic government, but U.S. officials have not made clear how the members will be chosen or when. They have offered only general pledges to create a process that would allow for broad representation of Iraqs both inside and outside the country.

But arguments have persisted over specific exile leaders. In particular, some defense officials, along with senior Pentagon adviser Richard N. Perle and former CIA director R. James Woolsey, have a long-standing relationship with Chalabi. They say his experience outside Iraq and his longtime commitment to the overthrow of Hussein and to other administration goals in the Middle East make him well-suited to play a leading role.

Among several alternatives, the State Department has suggested that the INC and five other anti-Hussein organizations be designated as part of a "conference" of Iraqi leaders, with other leaders to be added as more of the country is brought under U.S. control. When the balance is right, the conference could name an interim authority.

Pace rejected the suggestion yesterday that the arrival of Chalabi's group in the south would give the INC an unfair advantage in the process of setting up a new government.

"The fact that they may be from one section of the population or another at this point in time on the battlefield is not significant," he said. "I'm comfortable that once we free Iraq and give it to the people in Iraq, that they will be able to decide for themselves who should be their leaders and who should not."

Chalabi issued his own statement from Nasiriyah. "The war of national liberation which Iraqis have waged for 30 years is now nearing its end," he said. "We call on the Iraqi people to join with us in removing the final remnants of Saddam's Baathist regime."

Deputy Defense Secretary Paul D. Wolfowitz indicated yesterday that creation of the interim authority could take awhile, possibly more than six months. "Six months is what happened in northern Iraq," he said on "Fox News Sunday," referring to the time it took the Kurds to set up a territory after the 1991 Persian Gulf War. "This is a more complicated situation. It will probably take more than that."

Staff writer Peter Slevin contributed to this report.