WASHINGTON, June 26 — Senator Richard G. Lugar of Indiana, the ranking Republican on the Foreign Relations Committee and a steadfast supporter of the president, has conspicuously broken ranks with him on the Iraq war, warning that the United States’ standing in the world could be irreparably eroded if the White House does not change strategy soon.
“In my judgment, the costs and risks of continuing down the current path outweigh the potential benefits that might be achieved,” Mr. Lugar said Monday during a 50-minute speech on the Senate floor, which was delivered after nearly everyone in the Capitol had retired for the evening. “Persisting indefinitely with the surge strategy will delay policy adjustments that have a better chance of protecting our vital interests over the long term.”
In an interview with reporters on Tuesday, Mr. Lugar said President Bush had limited time to change the course of the war because of the 2008 presidential campaign.
“We’re heading into a very partisan era,” he said. “The president has the opportunity now to bring about a bipartisan foreign policy. I don’t think he’ll have that option very long.”
His remarks reverberated through Capitol Hill on Tuesday, picking up support from other Republican senators, even as the White House, which was not alerted about Mr. Lugar’s speech in advance, tried to minimize their significance.
At his daily televised briefing, Tony Snow, Mr. Bush’s press secretary, dismissed the idea that the White House might worry that Mr. Lugar’s statement would encourage fellow Republicans to join him in breaking with the president.
For months, Mr. Lugar has kept his skepticism about the president’s Iraq policy largely to himself, seldom offering anything beyond a hopeful wait-and-see statement. A soft-spoken cardinal of foreign policy, Mr. Lugar is known to his colleagues as anything but a bitter partisan, which made his remarks all the more stinging.
Senator George V. Voinovich, an Ohio Republican who also serves on the Foreign Relations Committee, echoed Mr. Lugar’s message in a letter to the president on Tuesday, a critique whose timing was coordinated to follow on the heels of Mr. Lugar’s.
“I am also concerned that we are running out of time,” Mr. Voinovich wrote in the letter.
Other Republicans also said their patience was waning.
“The one real disappointment is that the Iraqi government has not stepped up and fulfilled what we think is the role that they need to play,” said Senator Richard M. Burr, Republican of North Carolina. “If that doesn’t happen quickly, I’m sure more of us will come to the conclusion that Senator Lugar has.”
The White House worked vigorously to contain any political damage on Tuesday, hastily arranging a meeting this week between Mr. Lugar and the national security adviser, Stephen J. Hadley. The meeting was scheduled on Mr. Lugar’s turf, on Capitol Hill.
Administration officials privately conceded that should the images out of Iraq continue to be bloody in September, the White House will find it that much harder to maintain Republican support for the strategy, if not for the war itself. Officials have acknowledged that they are bracing for that eventuality, which they expect to play out when Congress begins debating military spending bills when lawmakers return to Washington after the Fourth of July break.
Democrats seized upon the remarks from the leading Republican senators, particularly Mr. Lugar’s, and said they were a sign that the tide is shifting in the protracted Iraq debate.
“I am encouraged by what he said and it just adds to the momentum for change,” said Senator Carl Levin of Michigan, chairman of the Armed Services Committee. “Hopefully he’ll take some very specific steps to implement what his words mean. They are powerful words.”
Mr. Lugar, 75, won re-election to his sixth term last year without opposition, the only Republican senator not to have a Democratic challenger. When Democrats won control of the Senate, he lost his chairmanship of the Foreign Relations Committee, but remains the ranking Republican on the panel.
In January, when Mr. Bush announced his plan to send more than 30,000 additional combat troops to Iraq, Mr. Lugar had his reservations. He and Senator John W. Warner, Republican of Virginia, aired their concerns during a private Oval Office session with the president.
Since then, Mr. Lugar has sided with the administration on every Iraq vote and has only occasionally voiced criticism during Foreign Relations Committee meetings. He said Tuesday that he had no intention of suddenly voting with Democrats, particularly in their efforts to limit war financing or set a timetable for withdrawal.
The White House and the Pentagon have implored lawmakers for patience until they receive an update in September from Gen. David H. Petraeus, the American commander in Iraq.
Mr. Lugar said he thought it was too late to begin devising an exit strategy. The United States is becoming diplomatically paralyzed in the Middle East and around the world, he said, and by September the presidential campaign would inflame the partisanship battle.
“The administration and Congress must suspend what has become almost knee-jerk political combat over Iraq,” Mr. Lugar said. “Those who offer constructive criticism of the surge strategy are not defeatists, any more than those who warn against a precipitous withdrawal are militarists.”
The White House did not offer a detailed response to Mr. Lugar’s remarks, but Mr. Snow said: “We take seriously his point of view because he is a serious guy. On the other hand, we also take seriously the efforts and the advice that the president has gotten from his commanders on the ground.”
By the end of the day on Tuesday, the White House also had a letter to contend with from Mr. Voinovich, who called on the administration to develop a comprehensive military withdrawal plan from Iraq.
“My heart has been heavy for a long time,” he said in an interview. “We’re talking $620 billion. We’re talking over 3,500 people killed. I have a picture of one of our marines that’s on my desk so I don’t forget, O.K.?”
The color photograph was presented to him by the father of an Ohio marine who was killed in Iraq.