Washington ? Expressing growing unease over the war in Iraq, a newly emboldened Senate voted overwhelmingly Tuesday to instruct the Bush administration to explain its strategy for completing the U.S. mission in Iraq and bringing American troops home.

Congress had shown great reluctance since the outset of the Iraq war to directly challenge the administration on its management of the conflict, in part for fear of being seen as insufficiently patriotic or supportive of the troops. Tuesday’s action seemed to signal that this period of quiescence is over, driven by the war’s falling popularity, and it follows by just days the president’s forceful counterattack on congressional war critics.

“Historians will look back on this day and say this was a turning point,” Sen. Chuck Hagel, R-Neb., told the Council on Foreign Relations. Calling the debate long overdue, Hagel said, “This is a significant step toward the Congress exercising its constitutional responsibilities over matters of war.”

The Senate voted 79-19 to require the administration to report to Congress on military operations in Iraq every three months, specifically on progress toward a troop withdrawal. In a nonbinding section of the legislation, the Senate urged that 2006 “should be a period of significant transition to full Iraqi sovereignty.”

However, lawmakers in a 58-40 vote decided against calling for a timetable for withdrawal. That measure, pushed by Democrats, would have required the administration to establish estimated dates for accomplishing certain milestones leading to pulling out the troops.

Whether the Senate’s language on Iraq policy survives House-Senate negotiations to reconcile the two versions of a defense spending bill remains to be seen. But whatever the outcome, the symbolism of the Senate action seems clear.

With the cost of the war exceeding $350 billion and 2,000 lives, polls show support for the U.S. military presence plummeting along with support for President Bush. Democrats, once fearful of speaking out against the war, have become newly energized.

“The minor good news is that Democrats are finding their voice and they’ve broken the taboo against talking about the war,” said Sen. Russ Feingold, D-Wis., the lone Democrat to begin pushing for the withdrawal timetable five months ago.

Senate Democratic Leader Harry Reid, of Nevada, accused the administration of engaging in a strategy that is “aimless” and “rudderless.” He added, “Today, you saw a vote of no-confidence on the Bush administration’s policy on Iraq.”

Bush is in Asia this week, and the White House had no immediate comment on the Senate vote.

But the president has recently accused his critics of playing politics with the war. “As our troops fight a ruthless enemy determined to destroy our way of life, they deserve to know that their elected leaders who voted to send them into war continue to stand behind them,” Bush said in Anchorage, Alaska, Monday.

It was a Democratic push to attach language on the Iraq war to a defense spending bill that forced Republicans to largely accede to their wishes. Senate Majority Leader Bill Frist, R-Tenn., and Armed Services Committee Chairman John Warner, R-Va., agreed to sponsor the Democrats’ amendment, minus the paragraph calling for a withdrawal timetable.

U.S. soldiers block a highway after a roadside bomb exploded Tuesday in Baghdad, Iraq. The Senate on Tuesday voted to hold the Bush administration more accountable for progress in the war in Iraq.

“The point is to send the strongest possible message to Iraqis,” Warner said.

Frist blasted his Democratic colleagues for advocating a “cut-and-run strategy” by pushing a timetable, which he called dangerous and irresponsible.

And he insisted that the amendment overall “is not a change in policy, not a change in tone. Our body (the Senate) remains where it’s always been – supportive of the president and supportive of troops.”

But even some conservative Republicans said the vote clearly conveyed Congress’s anxiety about the Iraq situation.

“For everyone to think Republicans are just on autopilot is not true,” said Sen. Larry Craig, R-Idaho.

The U.S. military has raised the notion of a draw-down of U.S. forces in the near future. Last summer Gen. George Casey, the commander of coalition forces, raised the prospect of bringing troops home sometime next spring.

Under the administration’s current plans, U.S. forces are ceding some authority to Iraqi units that are more capable, or located in parts of the country that are remote or have seen relatively few hostilities. Fifteen bases, most of them small, have been turned over to Iraq units in recent weeks.

About 200,000 Iraqi personnel have been trained by U.S. forces, but 84,000 of them are police officers capable of little more than basic law enforcement. Just one battalion – up to about 1,000 Iraq soldiers – is capable of fighting insurgents independent of U.S. forces.

Defense Secretary Donald Rumsfeld, asked about the Senate action during a press briefing Tuesday, said the Pentagon already supplies a raft of reports and briefings to Capitol Hill each month.

“I’m told that the Department of Defense and the Department of State send literally dozens of Iraqi-related reports to Congress each year already,” he said.

The Senate approved the Iraq policy language as part of a larger defense spending bill, which passed 98-0. The White House has threatened to veto the overall measure because it includes a prohibition against cruel, inhuman and degrading treatment of detainees and would standardize interrogation procedures employed by American troops.

Also on Tuesday, senators approved an amendment to allow detainees in Guantanamo Bay to appeal their status as enemy combatants as well as rulings by U.S. military tribunals to a federal appeals court in Washington.