A top Republican congressman has broken from his party in the final days of his House career, saying he believes the U.S. military assault on Iraq (search) was unjustified and that the situation there has deteriorated into "a dangerous, costly mess."

"I've reached the conclusion, retrospectively, now that the inadequate intelligence and faulty conclusions are being revealed, that all things being considered, it was a mistake to launch that military action," Rep. Doug Bereuter (search), R-Neb., wrote in a letter to constituents.

"Left unresolved for now is whether intelligence was intentionally misconstrued to justify military action," he said.

Bereuter is a senior member of the House International Relations Committee (search) and vice chairman of the House Intelligence Committee. He is stepping down after 13 terms to become the president of the Asia Foundation (search), effective Sept. 1.

The letter was reported by the Lincoln Journal Star in its Wednesday editions.

In 2002, Bereuter had spoken out in support of a House resolution authorizing the president to go to war.

Bereuter didn't answer questions Wednesday about the letter, but the campaign for Democratic presidential candidate John Kerry (search) said it was an indication of growing credibility problems facing the Bush administration.

"Anytime a member of the president's party directly challenges the president -- on any issue, especially war -- it's notable," said Kerry campaign spokesman Bill Burton.

Bush campaign spokesman Terry Holt said, however: "We feel good going into the convention that our party stands for a strong national defense and a forward-looking consensus on how to win the war on terror."

As for Bush's reaction, Holt said, "I don't believe the president has made any comments on the letter. Obviously, Congressman Bereuter has every right to communicate with his constituents and to share his views."

President Bush (search) has continued to argue the war was justified because Saddam Hussein represented a threat to the United States, his neighbors and the people of Iraq.

Most Republicans and top administration officials say the war was justified even though no weapons of mass destruction have been found.

However, after a scathing Senate Intelligence Committee report concluded in early July that intelligence agencies had provided false assessments of the Iraqi threat before the war, the panel's Republican chairman -- Sen. Pat Roberts of Kansas -- said Congress might not have approved the Iraq war had lawmakers known the truth.

Roberts said without an immediate threat that Saddam had and was trying to get weapons of mass destruction, military action against Iraq still could have been justified on humanitarian grounds, but that the battle plan might have been different from a full-scale invasion.

Bereuter said in addition to "a massive failure or misinterpretation of intelligence," the Bush administration made several other errors in going to war.

"From the beginning of the conflict, it was doubtful that we for long would be seen as liberators, but instead increasingly as an occupying force," he said. "Now we are immersed in a dangerous, costly mess, and there is no easy and quick way to end our responsibilities in Iraq without creating bigger future problems in the region and, in general, in the Muslim world."

Bereuter said as a result of the war, "our country's reputation around the world has never been lower and our alliances are weakened."

Sen. Chuck Hagel, R-Neb. -- who also has been a critic of the Bush administration's handling of the war -- is nonetheless co-chairing Bush's presidential campaign in Nebraska. "The reality is that we have 141,000 Americans fighting and dying in Iraq, and we must support them," he said.