U.S. soldiers waiting Tuesday for a sandstorm to pass in Karbala, 110km from Baghdad. (Photo: AP)
	British 'Desert Rats' posing with a painting of Saddam Hussein at the Ba'ath party headquarters in Basra on Tuesday. (Photo: AP)

Fifty percent of the air strikes being carried out by the allied forces were targeting Iraqi Republican Guard near Baghdad, said Air Force Gen. Richard Myers, chairman of the Joint Chiefs of Staff, said Tuesday at a Pentagon press briefing.

Defense Secretary Donald Rumsfeld, who also spoke at the briefing, said that U.S. and allied forces have now taken in "excess of 3,500 Iraqi prisoners."

The defense secretary said humanitarian assistance "food, water and medicine" is already being delivered. Still, after five days of ground combat, he sought to minimize expectations of a swift end to the war

"We're still, needless to say, much closer to the beginning than the end," Rumsfeld said.

Earlier Tuesday, a top U.S. commander said about 500 Iraqis have been killed in the last two days by U.S. Army infantry tanks and mechanized units as they swept through southern Iraq.

The estimate came from Command Sgt. Maj. Kenneth Preston of V Corps, who oversees the 3rd Infantry Division.

Preston said U.S. forces ran into "a lot" of Iraqi tanks and anti-aircraft weaponry and "thousands and thousands" of weapons around the city of Najaf.

"This could have been very ugly, but they're not very motivated," Preston said of the regular Iraqi army recruits. "I think a lot of them wanted to go home."

Many of the Iraqis appeared to have very low morale, he reported, adding that family members were seen picking up dead soldiers and taking them home for burial.

U.S. troops were stopping civilian vehicles and interrogating people, he added.

Asked about his division's plans, he replied: "Baghdad. That's where we're going, one step at a time."

The toughest fighting in the war with Iraq, however, still lies ahead, U.S. Chairman of the Joint Chiefs of Staff Gen. Richard Myers said Tuesday.

Speaking on ABC's "Good Morning America" program, the chairman of the Joint Chiefs of Staff anticipated resistance would get tougher the closer U.S. troops moved toward Baghdad. "We think the toughest fighting is ahead of us and we have known that all along and are we are preparing for that," he said.

Also Tuesday, a U.S. general said that coalition forces destroyed six GPS jamming systems they said Iraq had been trying to use to disrupt its satellite positioning equipment.

"We have noticed some attempts by the Iraqis to use a GPS jamming system that they have procured from another nation," Major-General Victor Renuart told a news briefing at the command headquarters in Qatar of the U.S.-led invasion.

"Actually we've been able to identify the location of each of those jammers and I'm happy to report that we have destroyed all six of those jammers in the last two nights' airstrikes."

"I am also pleased to say they had no affect on us. In fact we destroyed one of the jammers with a GPS weapon."

White House spokesman Ari Fleischer said Monday that Washington was very concerned at reports that Russian firms were providing GPS jamming equipment to the Iraqis.

Russia has denied supplying this equipment.

In fighting Tuesday, a large convoy of U.S. Marines crossed the Euphrates river and Saddam Canal at Nasiriyah on Tuesday, resuming a key advance toward Baghdad after fighting their way through the southern city.

South of Basra on Tuesday, British forces blocked an attempted breakout by up to 50 Iraqi tanks seeking to press southward from the edge of the city, destroying five to seven of them, a British naval commander said.

A British military spokesman said forces captured a top Ba`ath Party official in the city.

A northward advance on the far bank of the Euphrates could eventually form the eastward arm of a pincer movement on Baghdad, 375km north of Nasiriyah. To the west of the river, U.S. forces are only 100km south of the capital.

Aiming for Saddam Hussein's seat of power, coalition planes targeted Republican Guard forces just south of Baghdad in perhaps the largest assault to date on the Iraqi leader's highly trained troops, as U.S. officials warned that Iraq could use chemical weapons if soldiers crossed a "red line" ringing the capital.

At midday Tuesday, U.S. forces resumed bombings of Republican Guard troops south of Baghdad, a British official said.

Ground troops pressed toward Baghdad but many were but many were halted by a sandstorm near the holy city of Karbala, 50 miles south of the capital.

Also Tuesday, Britain announced a soldier from its Black Watch 1st Battalion was killed in fighting in southern Iraq, taking to 20 the number of dead and missing British troops since the war started last week. Another British soldier who was also fighting at Zubayr, near Basra, died Monday.

U.S. forces 80km rom Baghdad pounded military targets south of the Iraqi capital with howitzers and rockets Tuesday in an all-night artillery barrage that lit up the clouds like lightning.

Meanwhile, British forces - a day after coming under heavy attack - declared that Basra, Iraq's second largest, was now a "military target."

Coalition forces farther south were facing deadly ambushes and discovering that many Iraqi fighters had discarded their uniforms for civilian clothes.

U.S. General Tommy Franks said Saddam's regime was weakened but still issuing orders to military units - which are not always complying. Franks said his forces have captured 3,000 prisoners.

British: Umm Qasr 'safe and open'
The southern Iraqi port town of Umm Qasr, where U.S. and British forces have faced Iraqi resistance for days, is now "safe and open," a British commander said Tuesday. Brigadier Jim Dutton, commander of the British Royal Marines' 3rd Commando Brigade, told reporters he hoped the first ship bringing aid to Iraq would arrive within 48 hours.

American TV reports on Baghdad 'red line'
Allied troops' entry into Baghdad itself, however, could be met with a chemical attack.

American television stations CNN, NBC and CBS reported Monday that U.S. officials said the Iraqi leadership has drawn "a red line" around the map of Baghdad and that once American troops cross it, Republican Guards have been authorized to use chemical weapons, Reuters reported.

While a senior Pentagon source said he could not confirm
the reports, NBC said its information was coming from intelligence officials who based it on intercepts of Iraqi communications.

"It's believed once U.S. ground troops cross the line drawn roughly between Karbala and Al Kut, the Republican Guards are under orders to attack with chemical weapons," NBC said. CNN said the fact that the use of the weapons had apparently been authorized did not mean they would ultimately be employed.

British Prime Minister Tony Blair, who will meet with U.S. President George W. Bush at Camp David on Wednesday, told the British parliament that the "vital goal" was to reach the Iraqi capital as swiftly as possible.

Casualty figures after six days of combat:
The following are figures on the number of dead, missing and captured since the beginning of the Iraqi conflict:

American soldiers killed: 20

British soldiers killed: 18

(Neither American nor Iraqi officials have released a total number of Iraqi soldiers killed)

Iraqi civilian casualties: More than 200, according to Iraqi officials.

Iraqi prisoners of war: 3,000, according to the Pentagon.

American prisoners of war: 7, according to Iraqi officials. Two were captured Monday, Iraqi officials said, when an Apache helicopter was downed in central Iraq. Five were captured Sunday and shown on Iraqi television after an attack on an Army convoy.

American soldiers missing: 14, according to the Pentagon. That figure includes the five soldiers shown on Iraq TV and the two Apache pilots.

British soldiers missing: 2, according to the British military.