WASHINGTON — The White House and three powerful GOP senators reached an impasse Wednesday over a Bush administration plan to allow tough CIA interrogations, underscoring election-season divisions among Republicans on the high-profile issue of security.

In a direct challenge to President Bush, Sen. John Warner, chairman of the Armed Services Committee, said his panel would meet today to finalize an alternative to the White House plan to prosecute terror suspects and redefine acts that constitute war crimes. Warner, R-Va., said the administration proposal would lower the standard for the treatment of prisoners, potentially putting U.S. troops at risk should other countries retaliate.

The White House said Warner’s proposal would undermine the nation’s ability to interrogate prisoners, and arranged an extraordinary conference call for reporters in which the nation’s top intelligence official criticized Warner’s plan.

“If this draft legislation were passed in its present form, the director of the Central Intelligence Agency has told me that he did not believe that the (interrogation) program could go forward,” National Intelligence Director John Negroponte told reporters.

The unusually public dispute between the White House and the senators comes as Republicans face a robust Democratic challenge this November for control in Congress. The GOP is trying to sell voters on its tough stance on national security, and Bush has said legislation allowing him to prosecute terrorists is a key component to winning the war.

But the GOP deadlock left the fate of Bush’s proposal unclear.

The dispute echoed last year’s showdown between Bush and Sen. John McCain, R-Ariz., over legislation banning cruel, inhuman or degrading treatment of detainees. The White House threatened to veto that proposal, contending the language would hamstring interrogators, but eventually bowed to overwhelming congressional support for McCain’s measure.

McCain and Sen. Lindsey Graham, R-S.C., have joined Warner this year in opposing Bush’s bill.

Bush’s latest proposal would create military commissions to prosecute terror suspects and would redefine acts that constitute war crimes. Bush was forced to propose the measure after the Supreme Court ruled in June that his existing court system established to prosecute terrorism suspects was illegal and violated the Geneva Conventions.

The court ruled that Common Article 3 of the conventions, which sets a baseline standard for the treatment of prisoners of war, applies to members of al-Qaida — an assertion Bush had disputed. Since then, Congress and the administration have been drafting legislation that would authorize Bush to continue with the military commissions.