Wahoo, Neb. ? President Bush threatened Tuesday to veto legislation setting a date for a troop withdrawal from Iraq despite growing bipartisan calls in Congress for an end to U.S. participation in the war and sharp criticism of the Iraqi government.

As the Senate opened a new debate on the conflict, one of the president’s staunchest supporters bluntly said the administration had pursued the wrong policy for years after toppling Saddam Hussein.

“The strategy we had before was not the right strategy,” said Christopher Bond, R-Mo. “We should have had a counterinsurgency strategy.”

Asked later who bore responsibility for the error, Bond said, “Ultimately, obviously, the president.”

Democrats said Bush’s newest strategy was hardly a success, either.

Senate Majority Leader Harry Reid, D-Nev., said that since Bush ordered thousands more troops to Iraq last winter, “we’ve lost more than 600 troops, costing the American taxpayers more than $60 billion. The escalation has done nothing to bring the Iraqi government together. It’s done absolutely nothing to lessen the violence in Iraq.”

Two Democrats, Sens. Carl Levin of Michigan and Jack Reed of Rhode Island, back legislation to require a troop withdrawal to begin within 120 days and be completed by the end of April 2008.

A vote is expected next week, and Reid said nearly all Democrats support the proposal. Republican Gordon Smith of Oregon is a supporter, as well, and Olympia Snowe, R-Maine, said she may switch her position and vote for it, too.

House Speaker Nancy Pelosi said she would call for a vote on a similar measure by week’s end.

The Senate proposal appears to be short of the 60 votes needed to overcome a threatened Republican filibuster. Bush’s veto threat applied to any legislation that sets an arbitrary date for withdrawal “without regard to conditions on the ground or the recommendations of commanders.”

“Setting a date for withdrawal is equivalent to setting a date for failure,” he said in a written statement that employed terms similar to those he used earlier in the year when he vetoed legislation that set a target date for a withdrawal.

In a further sign of eroding GOP support, Sen. Elizabeth Dole, R-N.C., called for troops to come home next year.

“Simply put, our troops have been doing a great job, but the Iraqi government has not,” said Dole, the latest Senate Republican facing the voters in 2008 to switch positions on the war. “Our commitment in Iraq is not indefinite, nor should the Iraqi government perceive it to be.”