British troops battled paramilitary forces defending Basra Tuesday, their task made more urgent by reports that Saddam Hussein's die-hard defenders were firing on civilians.

Blinding sandstorms plagued the American-led advance on Baghdad.

Despite adverse weather in some parts of Iraq, U.S.-led warplanes bombed targets in the northern part of the country and briefly knocked government television off the air in the capital. U.S. troops in control of a vast Iraqi air base sealed 36 bunkers, earmarked as possible sites of Saddam's elusive weapons of mass destruction.

''We cannot know the duration of this war, yet we know its outcome,'' President Bush said after receiving an update at the Pentagon on the 6-day-old military campaign. ''We will prevail. …The Iraqi regime will be ended … and our world will be more secure and peaceful.''

Not surprisingly, Saddam saw it differently. State television carried what it described as a message from him to tribal and clan leaders, saying, ''Consider this to be the command of faith and jihad and fight them.''

There were few reliable details of the chaotic situation inside the southern city of Basra, Iraq's second-largest with 1.3 million residents. British journalists reported that residents were staging an uprising against pro-Saddam forces and that Iraqi troops were firing mortars at them.

A senior British commander, Maj. Gen. Peter Wall, said ''We don't know the scale'' of any revolt, but added, ''Of course we would be very keen to capitalize on it.''

The Iraqis denied all of it. ''The situation is stable,'' Information Minister Mohammed al-Sahhaf said in an interview with Al-Jazeera, an Arab satellite television network.

United Nations Secretary-General Kofi Annan and others have warned of a possible humanitarian crisis in the city. The International Red Cross said during the day that it had begun repairs at a war-damaged water-pumping station serving the city.

Thus far in the campaign known as Operation Iraqi Freedom, Americans said they had taken more than 3,500 Iraqi prisoners. There was no accurate death toll among Iraqi troops or civilians.

American losses ran to 20 dead and 14 captured or missing. The remains of the first two to die were flown overnight to Dover Air Force Base in Delaware.

A total of 20 British troops had also died, including two killed Monday by friendly fire.

Weather or not, the U.S.-led invasion moved ahead.

The U.S. Central Command, which overseas the war, announced the capture of an Iraqi military hospital used as a military staging area. Officials said Marines confiscated more than 200 weapons and stockpiles of ammunition and more than 3,000 chemical suits with masks, as well as Iraqi military uniforms. The Marines also found a T-55 tank on the compound.

Elements of the U.S. 3rd Infantry Division were about 50 miles from Baghdad and hit Republican Guard units defending the Iraqi capital with an all-night artillery barrage.

Thousands of other troops hastened - as much as the sandstorms would allow - to join them for the coming battle against Saddam's seat of power.

But some helicopters were grounded by the weather, and combat aircraft taking off from the USS Harry Truman returned a few hours later without dropping bombs on their targets.

Distant explosions could be heard in Baghdad, and efforts were underway to dig deeper defensive trenches around the city. Witnesses said Saddam's intelligence headquarters as well as a sprawling defense complex were hit in overnight bombing.

In the early hours of the invasion, military commanders had hoped that Basra's population would welcome the invading forces.

Instead, resistance by irregular and other forces has kept British troops from securing the city and paving the way for the flow of relief operations.

And in an about-face, a British spokesman told reporters, ''We are seizing tactical opportunities as they occur on our terms.''

Still, the spokesman, Col. Chris Vernon, described a situation of enormous difficulty. ''We are not firing into the center of the city because we cannot risk the collateral damage to civilians, even though we are being fired on by their artillery,'' he said.

In addition, Vernon said Iraqi troops are using the local population as human shields, marching them toward the British troops, then firing from behind them before retreating.

Bush, after receiving his war update, said U.S. forces were clearing approaches to the port city of Umm Qasr of Iraqi-laid mines. ''Coalition forces are working hard to make sure that when the food and medicine begins to move it does so in a safe way,'' he said.

Sensitive to international criticism that relief was slow in reaching Iraqis, the administration dispatched national security adviser Condoleezza Rice to the United Nations for a discussion of the issue. White House spokesman Ari Fleischer blamed Saddam for slowing the flow of goods by placing mines near Umm Qasr, adding, ''There's a massive stockpile that stands by and ready,'' he said.

British Prime Minister Tony Blair, who will confer with Bush this week at the presidential retreat at Camp David, Md., was at pains to prepare the British public for difficult days.

''There will be resistance all the way to the end of this campaign,'' he said.

Defense Secretary Donald H. Rumsfeld also made clear he didn't know how long the war would take. ''We're still, needless to say, much closer to the beginning than to the end,'' he said.

The war unfolded side by side with diplomatic maneuvering.

Speaking in Toronto, the American ambassador Paul Cellucci said Canada's refusal to send troops to the war effort has upset and disappointed the United States and caused a ''bump in relations.''

In Saudi Arabia, Foreign Minister Saud al-Faisal said his country has contacted the United States and Iraq with a peace proposal, and was awaiting a response.

He did not disclose the proposed terms. The Bush administration said it was not aware of any Saudi peace proposal, and there was no response from the Iraqi government.