WASHINGTON -- President Bush yesterday warned defiant Republican senators that he will close down a CIA interrogation program that he credited with thwarting terrorist attacks if they pass a proposal regulating detention of enemy combatants, escalating a politically charged battle that has exposed divisions within his party.

An irritated Mr. Bush, raising his voice and gesturing sharply at a Rose Garden news conference, excoriated legislation that a Senate panel passed Thursday that is intended to bring U.S. detainee practices in conformity with the Geneva Conventions. He insisted on legislation more specifically defining what is banned, so intelligence officers would not worry about being charged with war crimes.

"The professionals will not step up unless there's clarity in the law," Mr. Bush said. "So Congress has got a decision to make: Do you want the program to go forward or not? I strongly recommend that this program go forward in order for us to be able to protect America."

The president's threat to end the interrogation program seemed to make little impression on the Republican dissidents who have balked at his interpretation of the Geneva Conventions. Sens. John McCain, R-Ariz., and Lindsey Graham, R-S.C., two of four Republicans who voted against Bush's position Thursday, again rejected his logic after the news conference, and a fifth Republican senator, Olympia Snowe of Maine, joined the rebellion against the president.

"Weakening the Geneva protections is not only unnecessary, but would set an example to other countries, with less respect for basic human rights, that they could issue their own legislative 'reinterpretations,' " Mr. McCain said in a written statement. "This puts our military personnel and others directly at risk in this and future wars."

The dispute over how the United States conducts its ongoing battle with international terrorists dominated a question-and-answer session with the president that touched on a variety of high-profile issues 53 days before the midterm elections.

Mr. Bush lashed out at the United Nations for not moving more aggressively to stop genocide in Darfur, rejected what he called the "urban myth" that his administration has lost focus on finding al-Qaida terror chief Osama bin Laden and acknowledged that spiraling violence in Iraq has frustrated his hopes to begin bringing U.S. troops home this year. At a time when Mr. Bush hoped to be drawing distinctions between his own party and Democrats, though, he spent most of the conference arguing with fellow Republicans.

As Congress tries to wrap up business to go home and campaign, Mr. Bush is pressing for legislation endorsing his leadership against terrorism, including warrantless surveillance of overseas phone calls, military commissions to try enemy combatants and expansive rules permitting tough interrogations.

The most explosive debate centers on how the Geneva Conventions should apply to U.S. intelligence officers, who have captured, held and questioned terrorism suspects in secret overseas CIA prisons for years until the last 14 detainees were transferred recently into military custody at Guantanamo Bay, Cuba. The Supreme Court ruled in June that U.S. detainees fall under the Geneva Conventions, which require that wartime captives be "treated humanely" and ban "outrages upon personal dignity."

Mr. Bush wants legislation interpreting the conventions as barring "cruel, inhuman or degrading" treatment, adopting language from a McCain-sponsored law on prisoners signed last year. The conventions' broader "personal dignity" phrases, he argues, are so vague that they leave interrogators open to prosecution for a wide variety of techniques.

But Mr. McCain, Mr. Graham and Senate Armed Services Committee Chairman John W. Warner, R-Va., have rejected the Bush approach as too narrow, and as an invitation to other countries -- including Iran, Syria and North Korea -- to reinterpret the Geneva rules as they see fit if they ever hold U.S. soldiers.

"What is being billed as 'clarifying' our treaty obligations will be seen as 'withdrawing' from the treaty obligations," Mr. Graham said. "It will set precedent which could come back to haunt us."

Joining Mr. McCain and the other Republicans this week was former Secretary of State Colin Powell, who wrote in a letter that reinterpreting the Geneva Conventions would encourage other countries to "doubt the moral basis of our fight against terrorism."

Mr. Bush yesterday bristled at the criticism from his former top diplomat, calling it "flawed logic" and accusing Mr. Powell of equating U.S. tactics with those of terrorists, even though Mr. Powell's letter made no such comparison.