Hours after Bush went to Capitol Hill to urge fellow Republicans to back his proposals for putting terrorism suspects on trial, a divided Senate Armed Services Committee approved its own bill which it said would provide fair trials and meet the demands of the US Supreme Court that struck down Bush's original plan.
The committee also resisted Bush's bid to more narrowly define the Geneva Conventions' standards for humane treatment of prisoners, which Bush said was essential to enable the CIA to elicit valuable information from detainees.
The bill - pushed by chairman John Warner of Virginia and fellow Republicans John McCain of Arizona and Lindsey Graham of South Carolina - cleared the committee by 15-9 with support from Democrats and Maine Republican Susan Collins.
The full Senate will take up the issue as early as next week, meaning that Republicans could be in a bitter debate among themselves over national security issues which they view as key to keeping control of the House and Senate.
Democrats have stayed out of the fray, letting the Republicans show their divisions over Bush's handling of detainees.
Hoping to head off a rebellion over issues he insists are key to fighting the war on terrorism, Bush met with House Republicans in a closed session earlier in the day.
The committee bill would require that defendants have access to classified evidence used against them, limit the use of hearsay evidence and restrict the use of evidence obtained by coercion.
The main debate with the White House was over its efforts to write definitions of what would be inhumane treatment under the Geneva Conventions.
Administration officials said its standards were vague and must be clarified to protect CIA interrogators from prosecution and to allow the CIA's "high value terrorist detention" programme to continue.
But Warner, McCain and Graham said that would encourage other countries to interpret the protections to meet their own needs, which would backfire on US personnel in future wars.
McCain released a letter from Colin Powell, Bush's former secretary of state, that said the "world is beginning to doubt the moral basis of our fight against terrorism" and which said he opposed Bush's bid to redefine the Geneva Conventions that require humane treatment of prisoners.
The White House countered with a letter from Condoleezza Rice, the current secretary of state, saying Bush's plan would "strengthen US adherence" to the Geneva Conventions and would "help demonstrate to our international partners that we are committed to compliance" with the standards.