WASHINGTON - U.S. and British aircraft blasted Iraqi forces dug in around Baghdad yesterday, while allied leaders held a war summit in the Maryland mountains on the progress of the week-old invasion. "However long it takes ... Saddam Hussein will be removed," President Bush said after talks at Camp David with his main ally, Prime Minister Tony Blair of Britain.

Bush was responding to a question about growing speculation that the war could drag on for months. Stiffer-than-expected Iraqi resistance to the initial phase of the U.S.-led invasion has led some military officials to forecast a prolonged conflict that will require the deployment of additional troops.

Removing Hussein from power "could well grow more dangerous in the coming days and weeks," Defense Secretary Donald H. Rumsfeld told Congress. Echoing the president, Rumsfeld said it was unclear how long the war would last.

What is likely to be the toughest fighting yet lies immediately ahead, as American forces prepare for a crucial land battle against three elite Republican Guard divisions on the outskirts of Baghdad. Improved weather conditions allowed U.S. warplanes to attack heavily fortified Iraqi positions as well as tanks, artillery and armored vehicles in a prelude to ground fighting that appears to be at least a day or two away.

Iraq's defense minister, Sultan Hashem Ahmed, told journalists in Baghdad that he expects U.S.-led forces to have the capital surrounded within the next week or so. But he warned that the invaders would face bloody, block-by-block urban fighting that could last for months if they try to capture the city of 5 million residents.

Ahmed said the resistance that American and British troops have met on their swift advance toward Baghdad, especially from paramilitary forces, is "just the start of their troubles." He said Baghdad "will be their cemetery. We shall fight them for every spot, every place they come to."

The Iraqi regime, its forces hopelessly outgunned by the U.S. and British military, wants to prolong the fighting and increase the number of casualties until world opinion forces a halt.

"There isn't going to be a cease-fire," Rumsfeld told the Senate Appropriations defense subcommittee. He said later, "It will end at the point where that regime does not exist and a new regime is ready to go in its place."

U.S. military officials continue to maintain that the war is "on plan." Reported casualties remain light. The latest Pentagon count shows 28 Americans killed, 40 wounded, eight missing in action and seven held prisoner by Iraq.

A total of more than 90,000 American and British troops are inside Iraq, a number that is scheduled to grow to 225,000 over the next five weeks. Many of the most heavily fortified U.S. ground units won't be in place until mid-to-late April, however, because of delays caused by Turkey's refusal to allow American soldiers to cross their territory.

In an effort to tighten security in southern Iraq, the Pentagon is ordering 2,000 Marines from Africa into the area around Iraq's second-largest city, Basra, where British marines have been struggling to gain control for days.

There was more heavy bombing overnight in Baghdad. American air power is also targeting the area around the northern city of Tikrit, birthplace of Hussein, where another Republican Guard division is based.

Hussein made another appearance on Iraqi television, which has not yet been knocked completely off the air. The Iraqi leader was shown smiling at a meeting with members of his ruling Baath party.

Republican Guard

Elements of U.S. 101st Airborne Division rolled hundreds of miles into Iraq yesterday from neighboring Kuwait, reinforcing elements of the 3rd Infantry Division that have been running short of food, fuel and water. Front-line soldiers who have spent the past three days near the Shiite holy city of Karbala, about 50 miles from Baghdad, dug trenches to protect themselves against attacks by roving bands of Iraqi irregulars and possible artillery fire from forward units of the Republican Guard.

Military planners would like to destroy a significant portion of the Republican Guard's tanks and other armored vehicles, before ground fighting begins. The U.S. efforts, however, are complicated by Iraq's decision to position much of its equipment near civilian, religious or historically significant areas, U.S. officials say.

Under clear skies, American aircraft stepped up their attacks, using precision-guided bombs. Among the targets were communications facilities, including a telephone switching center, and surface-to-air missile sites inside Baghdad. As the attacks intensify, the risk of civilian casualties is increasing, despite the accuracy of the U.S. weaponry, because many of the targets are in residential neighborhoods.

Reports of battlefield successes - and setbacks - emerged from reporters traveling with U.S. and British units.

Near An Nasiriyah, two U.S. Marines were reported to have been critically wounded in a "friendly fire" incident between separate American units that left dozens wounded. The U.S. Central Command in Qatar would not immediately confirm the report.