U.S. warplanes attacked Baghdad's defenders with bombs and strafing fire Saturday in a thunderous prelude to a ground assault. Iraqis inflicted a new danger on the allies -- a deadly suicide attack -- and threatened to kill Americans on U.S. soil.

Anger, mourning and resolve emanated from both sides in a conflict taking a growing toll each day in the lives of combatants and civilians alike.

The international outcry grew, too. Pope John Paul II warned of a "religious catastrophe" stirring hatred between Christians and Muslims; Russian President Vladimir Putin also cast the war in catastrophic terms and said he would push for a negotiated solution.

But in Baghdad, Washington and along the war's many fronts, the talk was all of climactic battles to come.

"We are now fighting the most desperate units of the dictator's army," President Bush said before an hourlong meeting with his war council and an intelligence briefing.

Three-quarters of the allied airstrikes are now going after Republican Guard forces ringing Baghdad, Air Force Brig. Gen. Daniel Darnell said.

He said U.S. and British planes have attacked almost every military airfield in the country in the last week.

Intensified allied airstrikes on Saddam's best ground forces coincide with efforts by the Army's 3rd Infantry Division and the 1st Marine Expeditionary Force to consolidate their supply lines south of Baghdad before beginning a multipronged assault on the Republican Guard.

The intent is to severely weaken those forces so they will fall more quickly to American ground troops, minimizing U.S. casualties.

In a boost to coalition firepower, U.S. aircraft flew combat missions from Iraqi soil for the first time Saturday, when A-10 warplanes flew out of a captured Iraqi base to conduct strikes, CNN and Air Force Times correspondents at the base reported.

From the base, which CNN said was south of Baghdad, the A-10s can roam longer over Iraqi territory to hunt for Iraqi forces or protect allies.

There was no rest for pilots taking off from aircraft carriers in the Persian Gulf. Planes from the USS Constellation alone hit 40 targets in 24 hours.

Soldier as cab driver

Danger came to the 1st Brigade of the Army's 3rd Infantry Division in the guise of a cab driver.

A man, identified by Iraqi officials as a noncommissioned officer, drove his taxi to a U.S. checkpoint in south-central Iraq and waved for help. When soldiers approached, the car exploded and four Americans died.

"It looks and feels like terrorism," Maj. Gen. Stanley McChrystal said at the Pentagon. "It won't change our overall rules of engagement but, to protect our soldiers, it clearly requires great care."

Overall, more than 30 U.S. soldiers have died in the war.

In Tracy, Calif., Stacy Menusa, the wife of Gunnery Sgt. Joseph Menusa, said Saturday she had received word from the military that her husband was among the dead.

"I never thought it would be my Marine," she said.

Iraq's vice president suggested the attack at the U.S. checkpoint was not the work of a freelance fanatic but rather part of a coordinated effort to beat back invaders who cannot be defeated by conventional warfare.

"I am sure that the day will come when a single martyrdom operation will kill 5,000 enemies," Taha Yassin Ramadan said. Iraq's state television reported that Saddam Hussein posthumously promoted the bomber to colonel and awarded him two medals.

Ramadan held out the threat of Iraqi-sponsored terrorism on U.S. soil -- hinting of the very danger that Bush has tried to convince Americans that they face from Saddam.

"We will use any means to kill our enemy in our land and we will follow the enemy into its land," Ramadan said. "This is just the beginning.

"You'll hear more pleasant news later."

In the Iraqi desert, assault pilots in Apache helicopters from the 101st Airborne Division tallied the results of their first strikes of the war, conducted the night before. Among them: four Iraqi tanks, 15 vehicles, a fuel site and a communications tower.

"I don't think it's an adrenaline rush," said pilot Chris Montjoy, 28, of Clarksville, Tenn., reflecting on his first combat mission ever. "I think it's just scared."

U.S. Central Command officials said a coalition airstrike Friday night northeast of Basra killed an estimated 200 at a Baath Party assembly.

"We can find that these terror leaders are in fact having a meeting and then call in very precise strikes to destroy that," said Maj. Gen. Gene Renuart.

Northern front

Anti-Saddam Kurdish militiamen moved on two fronts in northern Iraq on Saturday, joining U.S. special forces in an attack on Islamic militants and advancing unopposed closer to the government-held city of Kirkuk and its oil fields.

Heavy machine-gun fire and bombardment were reported near positions of Ansar al-Islam extremists, who are alleged to have ties to al-Qaida terrorists and have come under sporadic attack by the United States for a week.

South of Baghdad, Marines battled Iraqi fighters in and around the Euphrates River city of Nasiriyah, at a junction of highways leading to Baghdad.

Renuart confirmed that U.S. forces had found bodies in an area near Nasiriyah where the Army's 507th Maintenance Company was ambushed by Iraqis a week ago. At least two 507th soldiers were killed, eight were missing and five were taken prisoner in that attack.

Renuart said investigators were sent to the site to identify the bodies and determine the cause of death.

British forces, at the gates of Basra since midweek, darted in and out of the southern city Saturday, destroying five Iraqi tanks and two statues of Saddam Hussein.

About 1,000 Saddam loyalists are holed up in Basra, where essential supplies are running low and Iraqi fighters have kept residents from leaving.

Anti-war protests continued worldwide.

About 30,000 people held hands in a 31-mile-long chain in northwestern Germany.

More than 10,000 people protested in Paris' Left Bank and youths beat a couple that complained about portraits of Iraq's leader held aloft by some marchers.

In the United States, thousands rallied against the war in Boston, New York and other cities. In Harrisburg, Pa., thousands turned out to support U.S. troops and speak out against anti-war groups.