WASHINGTON, Aug. 24 - Senior senators from both parties urged the Bush administration today to send thousands more American troops to Iraq and said many billions more dollars were needed to stabilize and rebuild that country and Afghanistan.
Senator John McCain, an Arizona Republican who was in Baghdad the day the United Nations headquarters was bombed, said that "at least another division," about 18,000 American troops, was needed. "Time is not on our side," he added on the NBC News program "Meet the Press."
Senator Joseph R. Biden Jr. of Delaware, the ranking Democrat on the Foreign Relations Committee, appearing on the same program, put the need at 40,000 to 60,000 more troops, a substantial increase over the current 139,000.
Senator Lindsey Graham, Republican of South Carolina, who accompanied Mr. McCain on his trip, said that while he considered the troop level in Iraq to be sufficient, billions of dollars of additional spending is required there and in Afghanistan.
"I am a fiscal conservative, and we're in debt," Mr. Graham said on "Fox News Sunday." "But the infrastructure needs in Afghanistan and Iraq are billions. We are underestimating the cost of this conflict, and we in the House and the Senate need to appropriate a lot more money."
Their comments came after a particularly violent week in Iraq, with the bombing of the United Nations headquarters in Baghdad on Tuesday, killing 23 people, and mounting fears of more such terrorist attacks.
L. Paul Bremer III, the chief American civilian administrator in Iraq, said on the Fox News program that scores of foreign terrorists were pouring into Iraq, adding that it was plausible to think that they were viewing it as a place to make "a last stand" against the United States.
Asked about one recent estimate that up to 500,000 troops might be needed in Iraq, Gen. Richard B. Myers, chairman of the Joint Chiefs of Staff, said on the CBS News program "Face the Nation," "No, I don't agree." American forces there, he said, are "supremely confident in their ability to deal with the threat."
But while the military is "stretched thin" around the globe, the general added, it could send more troops if commanders on the ground in Iraq made the request.
The Bush administration has said it hopes that other nations will provide more troops for Iraq but sees no need to send more Americans now.
"It's not a question of more troops," Mr. Bremer said. "It's a question of being effective with our intelligence, of getting more Iraqis to help us."
The quality of intelligence being offered by Iraqis has risen sharply, he added. In addition, he said, nearly 60,000 Iraqis have been recruited to help in police, border-guard and other security units.
The senators cautioned that failure to do more now could cause the costs of engagement in Iraq to rise significantly later. "We either spend the money now, we make the sacrifices now, or we pay much greater later," Mr. Graham said.
Mr. McCain said the occupying forces needed "to spend a whole lot more money" to restore basic services in Iraq.
Mr. Biden was sharply critical of the administration's reluctance to support a multinational United Nations force for Iraq, and he scoffed at its assurances that scores of other nations were sending troops. Now, he said, those countries were contributing an average 400 troops each.
He predicted that American forces would be in Iraq for three to five years, at a cost well over $100 billion.
But Mr. Bremer, while praising the United Nations contribution in aiding Iraqis, said it was "hard for me to see how the U.N. itself can play a further military role" in Iraq.
He and General Myers said the growing numbers of Iraqis in security positions had eased the demands on the occupying forces. Mr. Bremer acknowledged, however, that the trustworthiness of some of those Iraqis could be problematic. The possibility that Iraqi guards employed by the United Nations played a part in the bombing there, he said, was "certainly a working hypothesis - one of many."