Defense Secretary Richard B. Cheney said yesterday that Iraqi President Saddam Hussein probably will be able to "ride out" international economic sanctions and that war may be the only certain means to force Iraqi troops out of Kuwait.

Cheney also told the Senate Armed Services Committee that President Bush requires no additional authorization from Congress before sending U.S. forces into combat in the Persian Gulf.

The defense secretary's testimony appeared to deepen the split between the administration and key Democratic legislators over the proper role of Congress in the crisis and whether economic pressures against Iraq should be given more time to work. The legislators cautioned against rushing into a war that might be avoided by holding fast to sanctions and pursuing a diplomatic solution.

Meanwhile, the State Department announced yesterday that Iraq had agreed that any high-level meetings with the United States, as proposed by Bush last Friday, would be strictly bilateral and not include outside parties as Bush at first suggested. {Details on Page A27.}

According to the latest Washington Post-ABC News Poll, Americans overwhelmingly approve of President Bush's decision to seek talks with Iraq but are sharply divided over whether those meetings will produce a peaceful end to the stalemate in the gulf. Most of those polled doubt that the threat to use force against Iraq after Jan. 15 will persuade Saddam to withdraw from Kuwait. {Details on Page A27.}

"The real debate in this committee, and I believe in the country, is whether to continue to punish Iraq slowly with a U.N. embargo, or whether to punish Iraq with direct military action," Sen. Sam Nunn (D-Ga.), chairman of the committee, said at the start of four hours of testimony by Cheney and Gen. Colin L. Powell, chairman of the Joint Chiefs of Staff.

Nunn, who seemed to speak for most committee Democrats in advocating the continued "slow pain" of sanctions rather than war, also indicated later that the administration could be in for a battle on Capitol Hill next year if it seeks additional defense funds for military action in the gulf without resolving congressional concerns. "If the president decides to take offensive action," Nunn added, "the Congress should speak to that before action is taken."

The testimony by the nation's two senior military officials came after a week of warnings to the committee by retired military experts, who had urged caution and patience before committing the nation to war. But Cheney offered the most pessimistic view yet from the administration regarding the effectiveness of sanctions.

"We do not have an indefinite period of time to wait for sanctions to produce the desired result . . . " Cheney said. "Despite the pain he is inflicting on his own people, there is no indication that Saddam Hussein is open to a peaceful resolution of the problem he has created."

Cheney told the committee that "there is a price to be paid . . . for waiting for sanctions to work," including the continued destruction of Kuwait, deeper economic hardship for developing countries that traded with Iraq and the prospect of growing resistance among Arabs to the presence of U.S. forces on their soil.

Iraq's "command economy" has "the capacity to hunker down, if you will, and operate on a subsistence basis," Cheney said, adding for example that Saddam has increased farm prices 40 percent to boost agricultural production. Moreover, as Saddam's occupation army digs in ever deeper in Kuwait, "the military effort that might be required to get him out will be more difficult in the future than it is today," Cheney said.

Cheney suggested that sanctions were an uncertain means toward the main objective of getting Saddam out of Kuwait, while the full force of American combat power would be certain.

"It's far better to deal with {Saddam} now while the {international} coalition {against Iraq} is intact, while we have the United Nations behind us, while we have some 26 other nations assembled with military forces in the gulf, than it will be for us to deal with him 5 or 10 years from now when the members of the coalition have gone their disparate ways and when Saddam has become even better armed and more threatening," Cheney said.

But key Democratic legislators at the hearing disputed Cheney's argument that war may be the only acceptable way of resolving the crisis. "It seems to me that's almost a Chicken Little approach to our current policy," said Sen. John Glenn (D-Ohio). "The sky is falling and there is only one option, and that's war."

Powell's view on sanctions appeared to differ slightly from the defense secretary's. While voicing concern over whether "people will view us with the same seriousness that they view us now" if the United States delays going to war for a year or more, Powell conceded that the 400,000 U.S. troops now committed to the gulf could probably be maintained for a year without fully activating the reserves or reinstituting conscription.

He also noted that sanctions "would have something of a debilitating effect on {Iraqi military} capability" even as they cede the initiative to Saddam and give his forces more time to dig in. "What I would say is, we don't know if the sanctions will work," Powell added.

Nunn shot back: "If we have a war, we're never going to know whether {sanctions} would have worked, are we? That's the major point here."

Asked by Sen. Edward M. Kennedy (D-Mass.) whether Bush must seek congressional approval before attacking Iraq, Cheney replied, "I do not believe the president requires any additional authority from the Congress." Of the more than 200 occasions in U.S. history when presidents have committed U.S. military forces, the secretary added, "on only five of those occasions was there a prior declaration of war."

Kennedy sharply disagreed, and Nunn later said of Cheney: "I disagree with his reading of the U.S. Constitution. . . . {But} the more important question is whether this country can afford to go to war without a consensus that it's time to go to war."

Powell also provided one of the most succinct public accounts to date of the military philosophy underlying Operation Desert Shield. Noting that the political mission is to expel Iraq from Kuwait, Powell derided "alleged low-cost, incremental, may-work" military strategies, such as relying wholly on U.S. air power.

"The fundamental flaw in all such strategies is that it leaves the initiative in Saddam Hussein's hands. He makes the decision as to whether or not he will or not withdraw," Powell said. "Such strategies are designed to hope to win; they are not designed to win."

Powell's view, which he said is shared by the other members of the Joint Chiefs, is to amass overwhelming air, naval and heavy armor forces so that "the question {the Iraqis} will have to consider is, do they move it, or do they lose it?" The chairman also assured the committee that he had no intention of flinging U.S. troops as "cannon fodder" against Iraqi fortifications, but would use a strategy that exploited "our strengths against their vulnerabilities, avoids their strengths and protects us against attacks directed against our vulnerabilities."

The "Phase 1" deployment of U.S. forces, begun in early August, was completed by early November -- nearly a month ahead of schedule -- and 240,000 U.S. troops are now in the gulf, Powell said. Phase 2, announced by Bush on Nov. 8 and intended to give the United States an offensive punch by nearly doubling that force, is now underway.

Asked whether the multinational forces arrayed against Saddam have resolved their "command and control" problems, Powell said that Gen. H. Norman Schwarzkopf, the U.S. commander in Saudi Arabia, is sharing responsiblity with Saudi Prince Khalid. "That comes across, I know, not as cleanly as you would like or I would like," Powell said. "But it is not an arrangment that was designed in the war college. It's something that's been put together on the ground over time."

"It doesn't sound very good to me, general," Sen. J. James Exon (D-Neb.) replied.

Several senators cautioned Cheney and Powell against haste and overconfidence. "History is littered with the bones of optimists and soldiers who thought that they were headed for a short war," Sen. William S. Cohen (R-Maine) warned.

According to an alternative approach pushed by Nunn and various retired military officers who have appeared before his committee, the administration could complete its buildup of U.S. troop strength in the region from roughly 240,000 to 400,000, and then, in late January, begin rotating other troops into the region as replacements for those initially deployed in August.