Amid reports of the first popular uprising against Saddam Hussein since U.S. and British troops invaded Iraq last week, the Bush administration yesterday urged Iraqi civilians to stay indoors and refrain from attacking until the allies were in a position to help them.

The advice -- delivered by Secretary of Defense Donald H. Rumsfeld and U.S. commanders in the field -- contrasted sharply with the course pursued by President George H.W. Bush during the first Persian Gulf War in 1991, when he called on the Iraqi people to "take matters into their own hands."

A subsequent insurrection by Iraqi Shiites and Kurds was put down with great ferocity and bloodshed by Hussein's Republican Guard as the U.S. forces stood by, unwilling to intervene. Estimates of those killed ranged between 30,000 and 60,000.

This time around, both the United States and the local Shiite population of southern Iraq appear to have drawn important lessons from the February 1991 fiasco. Fearing retaliation by paramilitary forces loyal to Hussein and wary of President George W. Bush's resolve, Iraqi civilians have displayed little popular enthusiasm for the arrival of U.S. troops. And Washington is reluctant to endorse a premature popular rebellion that could end in tragedy.

"I am very careful about encouraging people to rise up," Rumsfeld said yesterday, as reports came in of a Shiite rebellion in Basra. "We know there are people in those cities ready to shoot them."

Before the war began, U.S. officials had painted a picture of a repressed Shiite population eagerly awaiting its hour of deliverance from three decades of dictatorial rule. As recently as Monday, deputy defense secretary Paul Wolfowitz predicted "an explosion of joy and relief" as soon as the people of Basra no longer felt an immediate "threat" from the Hussein regime.

But the first six days of the war have revealed a political situation in Iraq that is a lot messier and more complicated than many administration officials foresaw. Militiamen known as Saddam's Fedayeen are present in large numbers in Basra and other cities, terrorizing the local population and preventing U.S. and British forces from taking control. It is also becoming increasingly clear that among Iraqis, hatred for Hussein does not necessarily translate into love for America.

"The hawks said from the get-go that you would have Iraqis on the rooftops cheering the American as liberators. We haven't seen that," said Joseph Wilson, the last U.S. diplomat to leave Baghdad after the 1990 attack on Kuwait. "The big question for me is what do Iraqis hate most: Saddam, or the idea of foreigners invading their country, particularly foreigners blamed by many Iraqis for the economic devastation of their country?"

In deciding whether to encourage a Shiite uprising during the months leading up to the invasion, the Bush administration faced a delicate political dilemma. In military terms, a Shiite rebellion might have been a serious blow to Hussein. But there were political reasons to be wary of Shiite opposition groups that are closely allied to neighboring Iran.

The Shiites form half the population of Iraq but have been excluded from Hussein's Sunni-dominated government. They have long looked to Shiite Iran for political and spiritual leadership. During the insurrection of February 1991, the rebels set up a provisional Islamic government on the Iranian model; in subsequent years, Teheran has continued to offer dissident Iraqi Shiites financial support and a place of refuge.

The CIA and U.S. military intelligence also have been in touch with Shiite representatives, including their Teheran-based leader, Ayatollah Mohammed Bakr al-Hakim, over the past few years.

Plans for Hussein's overthrow developed during the Clinton administration envisaged a major role for the exile groups, including the creation of a haven inside Iraq from which they could foment unrest.

But those plans were radically revised after the Bush administration decided on a strategy of massive military force, and Al-Hakim recently told an interviewer that the United States had not shared any plans for Iraq's future with him.

Spokesmen for Iraqi exile groups complain that the Bush administration has failed to make full use of their expertise and their network of supporters inside Iraq. They add that Washington has focused much more attention on putting out feelers to potential dissidents within the regime than on encouraging popular uprisings.

"We have had some discussion with U.S. officials about the future of Iraq, but they never asked us for our help," said Hamid Bayati, London spokesman for the Supreme Council of the Islamic Revolution in Iraq, the main Shiite opposition group. "In fact, they ask us to keep our people away from the streets."

"We have not been involved in the military planning," said Entifadh Qanbar, Washington representative for the Iraqi National Congress, an umbrella opposition group. "In a liberation war, you need to get the public involved, and this has not been done in this war. Why not? Ask the Pentagon."

Iraqi exiles yesterday reported fighting in western sections of Basra between armed Fedayeen and ordinary citizens, sometimes involving "hand-to-hand combat." The clashes are taking place near the airport, they said, close to an area occupied by British troops who have been given the job of occupying Basra, and wiping out remaining Iraqi forces.

U.S. officials and Iraqi exiles say that memories of the failed 1991 uprising in southern Iraq are crucial to understanding the reluctance of many Shiites to welcome U.S. troops this time around. Despite the words of encouragement from President George H.W. Bush, the rebels found themselves fighting alone.

The U.S. military, under the terms of the armistice agreement with Baghdad, even permitted the Iraqi military to use helicopter gunships against the rebels, on the pretext that they were being used to transport Iraqi officials.

"The backing didn't materialize the way they thought it was going to materialize," recalled Air Force Gen. Richard B. Myers, chairman of the Joint Chiefs of Staff. "Hundreds of thousands were killed because they thought they had a chance for a popular uprising."

Briefing reporters at the Pentagon, Rumsfeld said he was reluctant to urge an uprising until he knew that British or U.S. troops could deal with paramilitary forces loyal to Saddam.

"People will rise up," he said. "But I hope and pray they'll do it at a time when there are sufficient forces nearby to be helpful to them rather than at a time when it simply costs their life."

Staff writer Peter Slevin contributed to this report.

Marines from the 2nd Battalion, 8th Regiment emerge from a corridor of an Iraqi hospital allegedly used for military purposes. Marines take part in an operation north from Nasiriyah. They then headed toward Baghdad after experiencing unexpected fierce fighting in this southern city.