U.S. forces have started rounding up Iraqi men in civilian clothes suspected of being involved with paramilitary squads that have been attacking them in southern Iraq and may ship some of them to the detention center at the U.S. naval base at Guantanamo Bay, Cuba, military officers said today.

Marines patrolling Nasiriyah and other areas of heavy fighting have already detained more than 300 men in civilian clothes, initiating roundups intended to cope with the danger of an enemy that opens fire and then melts back into the population. "You round them up -- that way they're not a threat," said a senior Marine officer.

The roundups are part of a shift to unconventional warfare by U.S. commanders in response to the hit-and-run attacks launched by the Saddam's Fedayeen and Baath Party militias on overstretched U.S. supply lines. The Americans have decided to emulate the British, who have used commando raids to counter resistance in southeastern Iraq.

While targeting some men in civilian clothes, U.S. officers are also trying to enlist Iraqis who are estranged from the government to help root out the militias in the towns along the highways leading to Baghdad. U.S. helicopters have been dropping leaflets over Nasiriyah soliciting assistance, and the top Marine commander in Iraq said today that he might eventually distribute captured weapons to Iraqi civilians to help them rise against President Saddam Hussein.

It is "incumbent upon us to eliminate the death squads keeping the people under their boot," said Lt. Gen. James T. Conway, who leads 85,000 Marines and British ground troops. To do that, he said, U.S. forces need good intelligence on the enemy's headquarters and leadership "and then we hit them . . . overtly and covertly."

U.S. officers say they recognize that roundups of men who appear to be civilians, and who may or may not be armed, will be among the most controversial tactics they could employ, and, if applied indiscriminately, could undermine their campaign to win the "hearts and minds" of the Iraqi people.

But they argue that they have little choice on a battlefield where they say the paramilitaries have been disguising themselves as villagers, opening fire after staging fake surrenders and intimidating others into fighting for them. Also, some U.S. forces have said they witnessed Iraqi militias pushing women and children into the line of fire. In the latest tactic to come to the attention of Marine officers, Iraqi guerrillas are stringing wire across roads at a height where it would decapitate machine gunners standing on top of passing military vehicles.

"These are bad guys and it would be insane to let them roam the battlefield," said a senior officer who did not want to be identified. "If we get a few who are innocent, I'm sorry, but we can't just let them go out there and start shooting at us again."

"This isn't something we even dreamed about doing," said another officer. "This has been forced upon us."

The officers said such roundups will not be arbitrary but will focus on the pattern established in the past 11 days. Putting aside the rules of engagement they devised before the war, military lawyers are drafting new criteria intended to guide front-line troops on when to take into custody Iraqi men -- and possibly women -- who are working with the militias and the Fedayeen. The Fedayeen is a militia group loyal to Hussein and created by his elder son, Uday.

Among those already targeted are men in civilian clothes who appear to be well fed and are hanging around dangerous areas from which other civilians have fled. Such men often have a military accouterment such as boots or an identification badge. Other indicators will be included in the guidelines for identifying suspects, but officers asked that details be withheld to avoid tipping off the militias.

"Seeing young, healthy males in the middle of a firefight makes you wonder what they're doing there," said the senior officer. "They're the only well-fed Iraqis in the area."

Suspects are being segregated from enemy prisoners of war, in part because they may have been tormentors of regular army soldiers now being held. The detainees will be treated like POWs, but without official status, until a hearing is held under Article 5 of the Geneva Conventions, officers said.

Such hearings, to be held in Iraq, will determine whether the detainees are released, held as POWs or declared illegal combatants. If they are labeled POWs, they will be held until the end of the war and then released along with other prisoners.

Any who are determined to have used civilians as human shields or otherwise violated the international covenants of war will be declared illegal combatants and sent to Guantanamo Bay or other holding facilities, to be detained with al Qaeda and Taliban fighters captured in Afghanistan, military officers said. "That guy's going to get the full treatment," said the senior officer.

Military lawyers said they were trying to decide how to hold the hearings and said they wanted to conduct them as quickly as possible to return any innocents caught up in the roundups to their homes, but they acknowledged they were ill prepared for the venture. "We're still figuring this out," said the senior officer, "because we thought we'd have mass surrenders, not this crap."

[Asked on CBS's "Face the Nation" whether the United States was satisfied that the seven known American POWs were being treated humanely by Iraq, Gen. Richard B. Myers, chairman of the Joint Chiefs of Staff, said, "I don't think we are yet." He said the United States is holding more than 4,000 Iraqi POWs.]

The issue of how to handle illegal combatants has stirred controversy since the war in Afghanistan. Islamic militants captured in Afghanistan and Pakistan were declared captives outside the normal rules of war and incarcerated for months at Guantanamo or elsewhere without trials or other legal rights.

The United States has sent 681 prisoners to Guantanamo Bay and released 21, for a current inmate count of 660, according to U.S. authorities.

The campaign in Iraq, expected to be fought as a more conventional war, did not at the outset appear likely to involve the same disputes. However, U.S. officers changed their thinking after seeing the tactics employed by Hussein's fighters, particularly in Nasiriyah, a crossroads city straddling the Euphrates River, and Umm Qasr, a deep-water port on the Persian Gulf.

[In Washington, a Pentagon official said "there currently is no plan" to send enemy prisoners of war from Iraq to Guantanamo.]

In a brief interview today, Conway, the commander of the 1st Marine Expeditionary Force, did not address the roundups but said U.S. commanders had been talking with local Iraqi leaders about joining the fight against Hussein's forces. "There are a number of leaders in this region resisting the regime," he said. "They want to believe in us, but they're scared." Referring to the Iraqi militias, he added, "These death squads are absolutely brutal. They shoot people in the face on a whim."

Other Marine officers said they are receiving more help from Iraqis in Nasiriyah who are eager to get rid of the Fedayeen and their allies. With these Iraqis pointing the way, the Marines said they have been able to identify some of the paramilitary leaders. Captured prisoners have also been providing intelligence during interrogations.

"In Nasiriyah, we have gotten a lot of support from the local population," said Lt. Col. David Pere, the senior watch officer at Marine headquarters here. "People are walking up to our line saying, 'You want to blow up that house three doors down.' " Marines tried to encourage that sentiment by handing out food, water and medical supplies, and commanders said they experienced less sniping. "Love is breaking out all over Iraq," Pere joked.

But they still took fire from a bridge in Nasiriyah today, and responded with AH-1 Cobra attack helicopters.

Conway said Hussein's command and control remains intact and Baghdad has been broadcasting false reports that the United States was negotiating a cease-fire leaving him in control -- a propaganda tool to convince dissident Iraqis that the United States would abandon them as it did after the Persian Gulf War of 1991.

U.S. commanders say they realize it will take time to earn the confidence of the Iraqis. Once that has been done, Conway said, "it's time for them to become more proactive in their own effort. . . . At that point, we would consider giving them limited amounts of weapons." He said he would distribute arms no larger than rocket-propelled grenades, or RPGs.

Some weapons that could be saved for that purpose were recovered in two major caches in Nasiriyah on Saturday. Marines reported finding more than 800 RPGs, 10,000 machine gun rounds, 300 mortar rounds and hundreds of artillery shells, as well as 300 chemical protection suits with masks and atropine injectors. Officers concluded that they had found a base for Iraq's 11th Armored Division.

Concerned about the presence of chemical protection and nerve agent antidotes, the Marines dispatched teams of specialists to comb through the arsenals today but concluded there were no weapons of mass destruction.

"We found so much ammunition that it would be too dangerous to the city to blow it in place," said Col. Ron Johnson, the operations officer for Task Force Tarawa, which found the caches. "We are going to have to transport it somewhere safe."

A U.S. Marine tries to push open a locked door while conducting a house-to-house search in rural areas on the southern edge of Nasiriyah. Marines from the 15th Expeditionary Unit are among U.S. forces fighting to seize control of areas in and around the crossroads city of Nasiriyah, where armed Iraqis pretend to surrender and then open fire.Iraqi civilians are taken from their homes and detained by Marines searching for weapons in an attempt to end the resistance slowing the allies' advance toward Baghdad.Marines conduct house-to-house search near Nasiriyah, where U.S. commanders tell of seeing Iraqi militias protect themselves by pushing women and children into the line of fire.