WASHINGTON - Sen. Hillary Rodham Clinton on Tuesday defended her vote to authorize war in Iraq amid growing unease among liberal Democrats who could determine the potential 2008 presidential candidate's future.

“I take responsibility for my vote, and I, along with a majority of Americans, expect the president and his administration to take responsibility for the false assurances, faulty evidence and mismanagement of the war,” the New York senator said in a lengthy letter to thousands of people who have written her about the war.

At the same time, she said the United States must “finish what it started” in Iraq.

Clinton and other hawkish Democrats have come under criticism from liberal anti-war activists, many of whom will hold sway over presidential primary contests. The former first lady, who is up for re-election in 2006, would likely be an early front-runner for the Democratic presidential nomination should she decide to seek it.

The 1,600-word letter was sent, mainly through e-mail, on Tuesday - a day before President Bush was to deliver a speech on his Iraqi policies. The president's approval ratings plummeted in recent months as the U.S. death toll and anti-war sentiments grew.

The debate has also put Clinton in a tight spot: generally viewed as pro-military, she is the most-watched member of a party that is increasingly turning against the war.

In her letter to voters, the senator cited prewar assurances from the White House that the United States would use the United Nations to resolve the issue of Iraq's purported weapons of mass destruction.

“Based on the information that we have today, Congress never would have been asked to give the president authority to use force against Iraq,” she said. Clinton stopped short of saying her vote was a mistake, the political path chosen by two other potential Democratic candidates - former vice presidential candidate John Edwards and Sen. Joe Biden, D-Del.

“Given years of assurances that the war was nearly over and that the insurgents were in their 'last throes,” this administration was either not being honest with the American people or did not know what was going on in Iraq,“ she wrote.

Clinton's allies billed the letter as her most comprehensive statement on the war to date.

“It is time for the president to stop serving up platitudes and present us with a plan for finishing this war with success and honor,” she wrote.

Clinton, who sits on the Senate Armed Services Committee, said earlier this month it would be a “big mistake” for U.S. troops to pull out immediately. She stuck with that line Tuesday. “America has a big job to do now. We must set reasonable goals to finish what we started and successfully turn over Iraqi security to Iraqis,” she wrote.