IMPEACH BUSH

As U.S. warplanes attacked targets in Basra yesterday, Bush administration officials acknowledged that their hands-off strategy toward southern Iraq in recent years has left them with little knowledge of the conflicts among competing Shiite groups there and few ways of influencing them.

President Bush yesterday hailed the decision of Iraqi Prime Minister Nouri al-Maliki to launch a full-scale military offensive against militias in Basra as a "defining moment" for his leadership. But other officials said the administration remains unsure of Maliki's motives and warned that the ongoing battle risks sending the country spiraling back toward the cataclysmic violence levels of 2006 and early 2007.

"This is a precarious situation," a senior official familiar with U.S. intelligence in southern Iraq said, with "a lot to be gained and a lot to lose." This official and others said that even as Maliki takes needed military action in Basra, he appears to be positioning himself and his Shiite political allies for dominance in provincial elections this fall.

Competition for power and resources in the oil-rich south has been ongoing for months among the Mahdi Army of Shiite cleric Moqtada al-Sadr; the Badr Corps militia of the Supreme Islamic Iraqi Council, the largest single party in the Iraqi parliament; and the breakaway Sadrist movement known as Fadhila. The Shiite groups are opposed and allied with each other in a tangle of national and local issues, with many divisions reflected in factions of the Shiite-dominated Iraqi security forces.

Although the Bush administration has tried to monitor the growing conflict in Basra, Iraq's second-largest city, "our intelligence in that area is far less than we would like. We don't have any forces there," the senior official said, adding that "we are operating with a good dose of opaqueness."

As outlined by several civilian and military officials, none of whom was authorized to speak on the record, a victory in Basra against what Bush described as "those who believe they are outside the law" could prove Maliki's mettle. "Basra's been a mess for a long time," said a U.S. official in Baghdad, "and everybody's said to Maliki, 'What are you doing about it?' "

But this official and others said that if the fighting in Basra leads to a breakdown in the cease-fire observed since August by the bulk of Sadr's forces elsewhere in the country, it could easily shatter the tenuous U.S. security gains of recent months.

The violence has already spread to Baghdad, where Iraqi and U.S. forces yesterday continued sporadic fighting with militia members in the sprawling eastern enclave known as Sadr City. Despite indications that many of the fighters were mainline Mahdi Army, U.S. officials chose to consider them members of "special groups" that have resisted Sadr's authority. To acknowledge otherwise would be to declare a de facto end to the cease-fire.

A renewal of significant violence in the capital and the surrounding area of central Iraq could lead to the collapse of U.S. security arrangements with former Sunni insurgents known as the Sons of Iraq. "All the same players and all the same weapons are still out there," said Stephen Biddle, a military expert at the Council on Foreign Relations who has advised Army Gen. David H. Petraeus, the top U.S. commander in Iraq.

"There is nothing preventing Iraq from going right back to October 2006 except voluntary agreements by the players. That's why Basra is so dangerous," Biddle said. "It's a real policy problem" for the administration, he said, "and the fact that there are no coalition forces on the ground in Basra is really coming home right now."

Biddle said that "if this thing collapses, there will be a lot of pressure [from the military] to halt further withdrawals of U.S. troops." About 9,000 troops have been withdrawn since last year, with an additional three brigades scheduled to come home by the end of July. An aide to Petraeus said yesterday there are "no plans on slowing anything at this point."

U.S. forces have stayed away from southern Iraq since they passed through rapidly on their march to Baghdad in the spring of 2003. The southern part of the country is overwhelmingly Shiite, and the U.S. focus during the first three years of the war was on the insurgency emanating from Sunnis backing Saddam Hussein and from the group al-Qaeda in Iraq.

At the same time, British forces had been given control of the south. While U.S. officers frequently disparaged British tactics as tepid, the administration was reluctant to criticize its key international ally. British forces eventually withdrew from the region and the city of Basra and are now largely confined, in reduced numbers, to a base near the Basra airport. In December, Basra became the latest province to be placed under complete Iraqi government control.

Even if they had wanted to move into the south at any point over the past five years, however, U.S. forces were already spread thin in the rest of the country. The sectarian warfare between Sunnis and Shiite militia groups that erupted in 2006 led Bush last year to deploy an additional 30,000 troops, which were concentrated in Baghdad and the surrounding area.

A National Intelligence Estimate last August warned that "intra-Shia conflict involving factions competing for power and resources probably will intensify as Iraqis assume control of provincial security" in the south. In Basra, it concluded, "violence has escalated with the drawdown of [British] forces there. Local militias show few signs of reducing their competition for control of valuable oil resources and territory."

Petraeus reported to Congress in September that both sectarian violence and al-Qaeda attacks had begun to drop sharply, the combined result of the U.S. troop "surge," Sadr's cease-fire and the Sunnis' changing sympathies. Asked by lawmakers about reports of increasing violence among Shiite groups competing for power and resources in Basra, Petraeus described it as an "Iraqi problem" with an "Iraqi solution."