U.S. President George Bush has announced that Donald Rumsfeld, architect of an increasingly violent and unpopular war in Iraq, is stepping down as Secretary of Defense.

He will be succeeded by former CIA director Robert Gates, who served under Bush's father.

The president described the 74-year-old Rumsfeld as a friend, a "patriot" and a ''superb leader'' in a time of change; but after lengthy discussion they came to the agreement that it's time for "new leadership'' at the Pentagon.

There have long been calls for Rumsfeld to resign, and the midterm election that cost Republicans control of the House and possibly the Senate ratcheted up those demands.

"This is a peace offering to the Democrats," Chuck Pena of the Independent Institute told CTV Newsnet. "Rumseld has been a lightning rod because of the Iraq war, and because of his personality and dealings with Congress."

Both Democrats and some Republicans have said the president should fire Rumsfeld and that Congress should have more involvement in the strategy for Iraq.

"The election has changed many things in Washington but it has not changed my fundamental responsibility," Bush told a White House press conference on Tuesday, "and that is to protect the American people from attack. As a commander-in-chief, I take these responsibilities seriously. So does the man who served this nation honourably for almost six years as our Secretary of Defense -- Donald Rumsfeld."

Rumsfeld had given no indication that he planned to step down in the wake of the midterm election.

Just two weeks ago, a combative Rumsfeld held a press conference at the Pentagon, accusing his critics and the media of trying to "make a little mischief" by trying to "find a little daylight between what the Iraqis say or someone in the United States says."

But the controversy over Rumsfeld's leadership wasn't just political. Over the weekend a series of strategically-timed editorials in the Army Times and other military publications called for him to resign.

"All along, Rumsfeld has assured us that things are well in hand," said the editorial. "Now, the president says he'll stick with Rumsfeld for the balance of his term in the White house. This is a mistake. ... When the nation's current military leaders start to break publicly with their defense secretary, then it is clear that he is losing control of the institution he ostensibly leads."

On Wednesday, Rumsfeld acknowledged his time as Secretary of Defence has been marked by criticism, but argued he has always listened to the opinions of others.

"These past six years have been quite a time. It calls to mind a statement by Winston Churchill, something to the effect of: 'I have benefitted greatly from criticism, and at no time have I suffered a lack thereof,'" he said.

Rumsfeld has long held to the strategy of handing over more control to the Iraqi government, and encouraging leaders there to make political progress on reconciliation and resource sharing.

The Gates appointment

Bush revealed he met with Gates last Sunday, two days before the midterm election. He said the appointment of Gates as Defense Secretary will bring a "fresh perspective" to the critical post and to the strategy in Iraq and on the broader war on terror.

"There is certainly going to be new leadership at the Pentagon and as I mentioned in my comments, secretary Rumsfeld and I agreed that sometimes it's necessary to have fresh perspective and Bob Gates will bring a fresh perspective. He will also bring great managerial experience," said the president.

But Pena argued the Bush administration will likely urge Gates to continue its current strategy in Iraq, and "stay the course," as the president told reporters Wednesday.

"Yes, he's an old hand in Washington, he's been around the block and served (under Bush's father). But he's being put in a position where he still has to implement the White House's policy," said Pena.

Gates' appointment would have to be confirmed by the Senate, whose majority will be decided one currently-contested election in Virginia.

In light of Rumsfeld's resignation, a reporter asked Bush if he still has full confidence in Dick Cheney, and whether the vice president will serve out the rest of his term. Bush replied, "Yes he does, yes he will."

Analysts and surveys of voters at polling places said opposition to the war was a significant contributor to the Democratic victory.

But Bush today pledged to finish the job he started in Iraq, and to stand by the people of Iraq.

"Do not be fearful," Bush said in reference to Iraqis. "As you take the difficult steps toward democracy and peace, America's going to stand with you. We know you want a better way of life, and now is the time to seize it."

Bush acknowledged to reporters that he realizes many Americans voted Tuesday night to register their displeasure with the lack of progress being made in Iraq.

But he said he believes most Americans and leaders from both political parties "understand we cannot accept defeat."

The president also expressed support for U.S. military personnel.

"Our nation is blessed to have men and women who volunteer to serve and are willing to risk their own lives for the safety of our fellow citizens," he said.

Rumsfeld was sworn in as the 21st Secretary of Defense under Bush in 2001. He had also served as the 13th Secretary of Defense in the Gerald Ford administration.

His political career began in the Dwight Eisenhower White House in the 1950s, shortly after his stint in the U.S. Navy from 1954 to 1957 as an aviator and flight instructor.

Robert Gates is the president of Texas A&M University, and a close friend of the Bush family. Having first joined the CIA in 1966, Gates served in the intelligence community for more than 25 years under six presidents. He served as CIA director for Bush Sr. from 1991 until 1993.

With files from The Associated Press