President George W. Bush's fragile political firewall against Iraq war critics was under siege as two Republican senators broke ranks with renewed calls Wednesday for changes in US strategy.
Senator Richard Lugar, a reluctant rebel and foreign policy expert, sent shockwaves through Washington by warning the US plan under way to "surge" nearly 30,000 troops into the country would not work.
He urged Bush to cooperate with lawmakers on the future of US involvement in the blood-stained country.
"The president may believe that he can simply continue on with or without the Congress, but I think he is wrong in that assumption," Lugar said in a pre-recorded interview with NPR radio news due to air Wednesday.
"My fear is that at some point we will have a withdrawal from Iraq that is very disorderly and not very well planned," he said in excerpts released by the station.
"That would be a tragedy for the troops, a tragedy for Iraq, a tragedy for us."
Fellow Republican George Voinovich, who like Lugar has resisted Democratic attempts to curtail Bush's war powers, recommended a disengagement from Iraq as the White House warned of a "very difficult summer" for US troops.
Lugar said the United States had vital interests in Iraq, which include stemming Iranian influence, preventing terrorists from using the country as a launch-pad and maintaining stability and US prestige in the Middle East.
But while warning against a total troop withdrawal, he said "the surge strategy is not an effective means of protecting these interests."
"Its prospects for success are too dependent on the actions of others who do not share our agenda. It relies on military power to achieve goals that it cannot achieve."
Voinovich, from Ohio, which has borne a heavy price in US combat deaths in Iraq, wrote to Bush to urge him to sketch a new war strategy.
"We must begin to develop a comprehensive plan for our country’s gradual military disengagement from Iraq and a corresponding increase in responsibility to the Iraqi government and its regional neighbors," he wrote.
"We must not abandon our mission, but we must begin a transition where the Iraqi government and its neighbors play a larger role in stabilizing Iraq."
White House spokesman Tony Snow downplayed Lugar's intervention, saying it was important to give the surge strategy time to succeed.
"Dick Lugar is a serious guy, so obviously you take it seriously. But on the other hand, again, he voted against the surge," Snow said. However, he warned of "a very difficult summer" ahead in Iraq.
Seventy-five US troops have died in Iraq this month alone, as the total death toll since the 2003 invasion has hit 3,552, according to an AFP count based on Pentagon figures.
Lugar's and Voinovich's comments hinted at a softening of Republican backing used by Bush as a bulwark against attempts by the Democratic-led Congress to end the war.
Democratic Senate leaders, lacking the 60 votes needed to force Bush's hand, argue Congress will only have a decisive impact when Republicans desert the president on the war.
Senate Democratic leader Harry Reid Tuesday seized on Lugar's remarks, as he mustered his party for a new assault on Bush's war powers.
"When we finally end this war, and the history books are written, I believe that senator Lugar's words yesterday could be remembered as a turning point," he said.
"But that will depend on whether more Republicans will take the courageous first step that Senator Lugar took."
Eyes are now on another veteran Republican, Senator John Warner -- as respected on military matters as Lugar is on foreign policy -- who may have the power to fracture Bush's Senate support base on the war.
Warner welcomed Lugar's stand as "an important and sincere contribution" to the Iraq debate, the Washington Post reported. He has expressed reservations over the Iraq war strategy but has not broken publicly with the White House so far.
In May, the top Senate Republican, Mitch McConnell, also predicted a sea-change in Iraq policy.
"I think the handwriting is on the wall that we are going in a different direction in the fall, and I expect the president himself to lead it," he said.
Democrats are setting new snares for Republicans in the run-up to September, when the US commander in Iraq General David Petraeus and US ambassador to Baghdad Ryan Crocker are due to brief Congress on progress in the surge strategy.
