The United States is committed to providing relief aid during any conflict in Iraq and to establishing a democratic regime for Iraqis after a war, President Bush said Saturday.

In a condensed version of a speech he had delivered on television Wednesday, Bush told his weekly radio audience he is determined to protect Americans from the threat he said Saddam Hussein poses.

At the same time, he sought to assure critics the aim of the United States is not the conquest of an Arab, oil-rich state, but an improvement in the lives of ordinary Iraqis.

The president said a military conflict could prompt Saddam, the Iraqi president, to use civilians as human shields for his military facilities, foment ethnic strife, destroy oil fields or deploy chemical or biological weapons.

"It will be difficult to help freedom take hold in a country that has known three decades of dictatorship, secret police, internal divisions and war," Bush said. "Yet the security of our nation and the hopes of millions depend on us, and Americans do not turn away from duties because they are hard."

In southern Iraq, U.S. warplanes bombed three mobile air-defense radars and an anti-aircraft missile system Friday, the U.S. Central Command said. U.S. pilots struck the equipment after Iraq moved it into the southern flight-interdiction zone near An Nasiriyah, about 170 miles southeast of Baghdad, Central Command said.

Friday was the fourth day in a row that American warplanes bombed targets in the "no-fly" zones over southern and northern Iraq.

U.S. forces also dropped 120,000 leaflets Friday in and around Basra, Iraq's second-largest city, about 35 miles from the border with Kuwait. Central Command said the leaflets directed Iraqis to U.S. military propaganda radio broadcasts, urged Iraqi troops to abandon their weapon systems and warned Iraqi troops not to use weapons of mass destruction.

On Saturday, European Command fliers from Incirlik Air Base in Turkey took the psychological warfare propaganda campaign to the northern zone. The command said its flights dropped 240,000 leaflets on two locations about 10 miles northeast of Mosul.

"Both locations have a history of Iraqi anti-aircraft artillery flying on coalition jets," a command statement said. The leaflets warned of immediate retaliation against hostile action toward U.S. and British planes enforcing the no-fly rules to keep Iraqi warplanes from flying against Kurds in northern Iraq.

In recent days, Bush has broadened his rationale for war in his public statements in the face of growing worldwide opposition.

The president, who was spending the weekend at Camp David, Md., made his recorded remarks as millions of anti-war protesters prepared to again take to the streets in cities around the world.

U.S., British and Spanish negotiators also were struggling to find the necessary support in the U.N. Security Council for their resolution authorizing the use of force to disarm Iraq.

Bush conferred by phone Friday with Dutch Prime Minister Jan Peter Balkenende, one of the leaders who has joined Bush's "coalition of the willing."

White House spokesman Ari Fleischer played down Russian Foreign Minister Igor Ivanov's comment that Moscow was prepared to use its veto against the resolution in the council.

"It's not an indication that there will be a veto," Fleischer said, adding that previous U.N. negotiating sessions produced similar ups and downs, with ultimate success for the U.S. position.

Fleischer also outlined Bush's conditions for avoiding a war that seemed to be viewed in the administration as all but inevitable: "Complete and immediate and total" disarmament as well as a change of leadership in Iraq.

Regime change has been U.S. policy since the Clinton administration, but is not part of any U.N. resolutions. The Bush administration has at times de-emphasized the need to change regimes, saying it was possible but not likely that Saddam could change the nature of his government by disarming.

But on Friday, Fleischer left little wiggle room. "It's disarmament and regime change," he said.

Full disarmament includes the destruction of chemical and biological weapons that Iraq possessed when weapons inspectors left Baghdad in the mid-1990s -- or proof that the weapons have been destroyed, Fleischer said.

"Every time (Saddam is) under pressure, he tries to relieve the pressure by disarming just a touch, just a little, playing the game, playing the deception," the spokesman said.

In his address, Bush said food, medicine and relief supplies such as blankets and water are being readied to supply to Iraqis in wartime. He also promised the United States would take the lead in destroying weapons stockpiles and protect Iraq's natural resources.

"This dictator will not be allowed to intimidate and blackmail the civilized world or to supply his terrible weapons to terrorist groups who would not hesitate to use them against us," Bush said.

"But America's cause is always larger than America's security. ... The lives and freedom of the Iraqi people matter little to Saddam Hussein, but they matter greatly to us."