The defections, which were set off by a major policy address Monday on the floor of the Senate by the ranking Republican on the chamber's Foreign Relations Committee, Richard Lugar, suggest that patience for Bush's approach among his own party is fast running out.

They also coincided with a new poll released this week by Newsweek magazine which found that public approval of Bush's handling of Iraq has reached an all-time low of 23 percent.

The same poll found that Bush's general approval ratings have also reached an all-time low of 26 percent, near the post-World War II record set by Richard Nixon shortly before his resignation in 1974.

The White House has argued that lawmakers should not push for any change in U.S. policy before at least September. That is when Gen. David Petraeus and the U.S. ambassador in Baghdad, Ryan Crocker, are scheduled to present an evaluation of the effectiveness of the "surge" – a counter-insurgency plan that since February has added 30,000 U.S. troops to the 135,000 already there in order to curb sectarian violence and encourage national reconciliation.

In recent weeks, both the Pentagon and the White House have appeared to retreat from that date, arguing that any assessment of the surge made in September was likely to be premature and thus suggesting that the current strategy be give more time.

Those suggestions may be precipitating what looks increasingly like a Republican revolt. Initiated by Lugar, it has been endorsed by Ohio Sen. George Voinovich and praised by Virginia Sen. John Warner, a key Republican leader on national security issues and former chairman of the Senate Armed Services Committee.

"I hail what he did," Warner said Tuesday, adding that he expected a number of Republicans to endorse Lugar's position during the debate over the 2008 defense appropriations bill next month. His office indicated that he would likely offer a detailed amendment to the bill laying out a change of strategy. After the July 4 recess, he said, "You'll be hearing a number of statements from other [Republican] colleagues."

Despite long-held reservations about the administration's policy in Iraq, Lugar, who served as the highly respected chairman of the Foreign Relations Committee before Democrats swept last November's elections, has consistently voted with the administration against Democratic efforts to set a timetable for the withdrawal of U.S. combat forces, as have Warner and Voinovich.

While, in his speech, he rejected the option of a "total withdrawal" of U.S. forces from Iraq, Lugar stressed that a "tactical drawdown," coupled with a much greater focus on regional diplomacy, including a credible effort to resolve the Arab-Israeli conflict, was an urgent necessity in light of the rapidly fading public support for Washington's continued engagement in Iraq.