A sandstorm made the going tough Tuesday as coalition troops continued their trek toward Iraq's capital city.

Soldiers were, however, able to continue to make progress in Operation Iraqi Freedom.

The sandstorm reduced visibility to only a few feet and two combat missions from two aircraft carriers were called off and two Army divisions were left at a standstill.

Most of the fighting occurred near the city of Basra, which is south of Baghdad.

Unconfirmed reports said Iraqi troops began firing mortars at civilian protesters in an uprising in Basra's streets. Meanwhile, coalition forces fired missiles at Iraqi soldiers.

British spokesman Col. Chris Vernon said Iraqi units were firing on British soldiers from behind a shield of civilians.

The British were massing tanks, vehicles and troops just outside the city in preparation to enter and liberate it.

Earlier Tuesday, British troops captured one Baath Party official and killed at least 20 Iraqi soldiers from irregular troops at a Baath party headquarters in Az Zubayr.

Hussein is a member of the Baath political group.

Two British Soldiers were killed at Az Zubayr, which is a navy port not far from Basra.

British Prime Minister Tony Blair reported that coalition troops had much of western Iraq in control and had managed to hold an essential southern port.

He also confirmed that allied forces had launched air attacks on Mosul and Kirkuk, both northern oil centers, and Hussein's hometown of Tikrit.

Troops were also headed to the Euphrates to help maintain two bridges.

As coalition forces get closer to Baghdad, they will have to face the Medina division of Hussein's Republican Guard.

&uot;This will plainly be a crucial moment,&uot; Blair said.

Defense Secretary Donald H. Rumsfeld agreed saying the confrontation with the Republican Guard is &uot;where the difficult task begins.&uot;

U.S. helicopters began firing at the Medina division on Monday, but soon withdrew after they were answered with heavy ground fire.

Before aborting, however, the helicopters destroyed 10 Iraqi tanks.

In other developments, U.S. Central Command confirmed that an American F-16 fired on a U.S. Patriot missile battery after the battery's radar locked on the plane.

Although there were no casualties, this marks the second time Patriot batteries have failed to distinguish between hostile and friendly targets.

Once again, coalition forces in the south have been set back by several attacks from Iraqis disguised as civilians.

Scattered fighting drove firefighters away from burning oil fields, but Umm Qasr remains securely in coalition hands.

Humanitarian aid will begin after the waterways have been checked for mines.

In Ah Nasiriyah, a vital location because of its bridges across the Euphrates, Navy pilots attacked Iraqi artillery and ammunition posts.

At press time, the largest battle of the war was under way at Karbala in north central Iraq.

It was estimated that 300 Iraqi soldiers had been killed.

Cheyenne Martin can be reached at cheyenne.martin @troymessenger.com