Questions about U.S. troop strength in Iraq have heightened since the truck bombing of U.N. headquarters in Baghdad last week that killed the United Nations' top envoy and at least 23 others.
About 150,000 American troops are in Iraq, along with 20,000 soldiers from Britain and other coalition countries. Sen. Joseph Biden, D-Del., cited some outside estimates that an additional 40,000 to 60,000 soldiers would be needed in Iraq.
"In order to get those, we need a U.N. resolution authorizing them. We don't have to have these folks under blue helmets (U.N. command). They can be under U.S. command," said Biden, senior Democrat on the Senate Foreign Relations Committee.
"We have to evaluate whether we have enough people, whether we have the right kind of people and whether we are spending enough money, and I think it's appropriate to make that evaluation," Sen. John McCain, R-Ariz., said last week.
But L. Paul Bremer, the U.S. civilian chief in Iraq, and Gen. Richard Myers, chairman of the Joint Chiefs of Staff, cited better intelligence and increased cooperation with Iraqis as keys to countering the rising number of terrorist attacks that have hampered rebuilding efforts.
In other developments:
Early Monday, two Iraqis were wounded when their vehicle attempted to avoid a U.S. checkpoint near Kirkuk, a military spokesman said. The soldiers manning the checkpoint opened fire and disabled the vehicle, she said. The Iraqis were being treated and were detained. Their wounds were not serious, she said.
An American soldier told an AP reporter Monday that the Republican Bridge over the Tigris River in central Baghdad had been closed for an hour Sunday night after U.S. forces discovered a bomb. He refused to give any other details.
In Najaf on Monday, mourners buried three guards who were killed in a bomb attack Sunday on the house of Mohammed Saeed al-Hakim, one of Iraq's most important Muslim Shiite clerics. He was among a group of three top Shiite leaders who were threatened with death by a rival Shiite cleric shortly after Saddam was toppled April 9.
The U.S. invaded Iraq using a force less than half the size of what it deployed in 1991 for the first Gulf War. However, its objective — occupying the entire country — was more ambitious than 12 years ago when it sought only to drive Iraqi forces from Kuwait. A total of 147 U.S. soldiers died in that war.
Some soldiers' families have been blunt saying changes must be made to better protect their loved ones serving in Iraq.
"They need to get more help (for the troops) or maybe get them out of there," said Ronda Quarterman of Galesburg, Illinois, whose son Chad is an infantry soldier in Iraq. "We're concerned that (Bush) said it is over when we still have guys that are being killed."
Myers said on CBS News Face the Nation that Gen. John Abizaid, the U.S. military commander in Iraq, hasn't asked for more troops, but the Pentagon would consider any such request.
U.N. Secretary-General Kofi Annan warned Friday that the United States' attempts to bring in soldiers from other countries to bolster its troops were likely to fail unless Washington agrees to a U.N.-authorized force that shares decision-making with Coalition forces.
At least some U.N. control is a condition that France, India and other nations have insisted on before sending troops.
Bremer told Fox News Sunday it was "hard for me to see how the U.N. itself can play a further military role because the U.N., in my experience, normally insists on commanding its own troops."
Bremer said all military forces should remain under command of the U.S.-led coalition, although "the U.N. clearly has a vital role to play in the reconstruction of Iraq."
Secretary of State Colin Powell said on a visit to the United Nations on Thursday that the United States would not cede any military power as France and other nations have demanded.
An Australian newspaper says Australia is resisting American requests for a fresh contribution of troops to Iraq as the security situation there deteriorates.