By Bradley Graham
Washington Post Staff Writer
Thursday, April 8, 2004; Page A01

U.S. forces have suffered their bloodiest week in Iraq since just before the fall of Baghdad a year ago, reporting 40 combat deaths in the seven days from March 31 to April 6.

Unlike earlier spikes in casualty figures, notably ones last autumn that resulted from a few helicopter crashes, the latest jump reflects a broad range of incidents, from fierce firefights to roadside bombs. U.S. military deaths in Iraq since the invasion now total 635, including 444 caused by hostile fire. The number of wounded has reached 2,988.

As a sign of growing Pentagon concern about deteriorating security, Defense Secretary Donald H. Rumsfeld raised the possibility yesterday that some U.S. troops scheduled to leave Iraq in the next few weeks might be kept in place to counter the mounting unrest. Many of the U.S. troops who died in the past week arrived only recently in Iraq, part of a rotation of forces that began earlier this year to replace war-weary veterans.

While plans have called for the U.S. troop level to drop to 115,000 by June, about 135,000 are now in Iraq as arrivals overlap with those due to leave.

"We're taking advantage of that increase, and we will likely be managing the pace of the redeployments to allow those seasoned troops with experience and relationships with the local populations to see the current situation through," Rumsfeld said.

Another senior defense official said later that no decision had been made to extend tours, which would break a Pentagon commitment to limit troop stays in Iraq to one year. Army Gen. John P. Abizaid, commander of U.S. military operations in the Persian Gulf region, is reviewing options for bolstering emergency response forces, focusing initially on shifting some units closer to trouble spots, the official said.

The recent surge in violence has involved both a rise in attacks by Sunni insurgents and a new militant campaign by Shiite forces loyal to cleric Moqtada Sadr. At a Pentagon news conference, Rumsfeld and Air Force Gen. Richard B. Myers, chairman of the Joint Chiefs of Staff, disputed characterizations of the violence as a popular uprising. They said battles have involved relatively small numbers of militants, estimating the size of Sadr's militia at 1,000 to 6,000 fighters.

"There's nothing like an army or large elements of hundreds of people trying to change the situation," Rumsfeld said. "You have a mixture of a small number of terrorists, a small number of militias, coupled with some demonstrations and some lawlessness."

Rumsfeld also rejected the notion that the intensified fighting represented "a turning point." But he called it a "test of will," saying the militants were engaged in a "power play" before the planned June 30 handover of sovereignty to an Iraqi government.

While vowing "robust military action" to restore calm, Rumsfeld warned Iraqi pilgrims that holy cities were potentially dangerous during the upcoming Shiite holiday of Arba'in. He said Iraqi authorities had asked that U.S. forces stay away from the cities and so the troops will not be in position to protect pilgrims.

The Marine Corps, with 25 dead, suffered the largest share of military deaths in the seven days ending April 6. The Marines took charge last month of a large area west of Baghdad that has been a hotbed of Sunni resistance.

In one set of battles Tuesday in Ramadi, 12 Marines died engaging Sunni militants, and four have died since last weekend in operations to secure Fallujah, where four civilian contractors were killed March 31 and their bodies mutilated.

The U.S. Army has reported 15 deaths. Eight occurred last weekend in Baghdad battles with Shiite militants. Other soldiers perished one by one in attacks in Baghdad, Kirkuk, Balad and Mosul, victims of rocket-propelled grenades or bombs buried along roadways.

Bryan Whitman, a senior Pentagon spokesman, said some of the rise in U.S. combat deaths could be linked to U.S. forces stepping up offensive operations over the past week.

"We're taking the fight to the enemy," he said. "Clearly, there are dangers associated with doing that."

Other defense officials, speaking on the condition of anonymity, said the number of Iraqi militants killed as a result of U.S. action has far exceeded the number of American dead. But the officials declined to provide figures for Iraqi casualties. News reports from Iraq have put the number at more than 100.

In a departure from casualty reporting practices by U.S. forces in Iraq over the past year, the Marine Corps adopted a policy last month of disclosing only the number of Marines killed on any given day. Marine casualty announcements now generally list the cause of death simply as "enemy action." Occasionally a phrase is added saying the deceased were engaging in "security and stability operations" when they died.

By contrast, announcements of Army war dead, while hardly expansive, continue to give at least the time of day that an attack occurred, the nearest town and the nature of the attack -- an explosion of a roadside bomb, for instance, or small-arms or grenade fire.

In an explanatory note often posted with its death announcements, the Marine Corps calls the lack of detail a "force protection measure," saying the release of more information could aid enemy fighters "in assessing the effectiveness or lack thereof with regard to their tactics, techniques and procedures."

But the Marine policy has drawn objections from some defense officials, who have argued for making the Marine announcements consistent with Army ones.

"It's a matter of reaching a balance between the amount of information you provide the U.S. public and the amount you end up disclosing to the enemy," said Whitman, the Pentagon spokesman. "There's an ongoing discussion about where that appropriate balance lies."

Researcher Robert E. Thomason contributed to this report.