Mr Rumsfeld has not discussed the controversy with the White House and was not considering resigning, said Eric Ruff, a spokesman for the defence secretary.
White House spokesman Scott McClellan said Mr Bush believes Mr Rumsfeld "is doing a very fine job during a challenging period in our nation's history.
"We are a nation at war and we are a nation that is going through a military transformation. Those are issues that tend to generate debate and disagreement and we recognize that," he said.
Generals take aim
Retired major general Charles Swannack, a former commander of the 82nd Airborne Division in Iraq, and retired major general John Riggs, also a former division commander, were the latest to call for Mr Rumsfeld to go.
"I feel he's micromanaged the generals that are leading our forces there to achieve the strategic objective," Maj Gen Swannack told CNN. "I really believe that we need a new secretary of defence."
Maj Gen Riggs told The Washington Post "everyone pretty much thinks Rumsfeld and the bunch around him should be cleared out."
Analysts say the five retired generals are giving voice to the pent up resentment of active duty leaders, many of whom perceive Mr Rumsfeld as arrogant and dismissive of military advice.
"My sincere view is that the commitment of our forces to this fight was done with a casualness and swagger that are the special province of those who have never had to execute these missions -- or bury the results," marine lieutenant general Gregory Newbold, operations director of the Joint Staff during the Afghanistan war and during early planning for Iraq, wrote in Time magazine.
Rumsfeld defended
Another retired general, who also served in Iraq, however, weighed in to say Mr Rumsfeld was an effective defence secretary, although one who could be tough to deal with.
"Dealing with Secretary Rumsfeld is like dealing with a CEO," said retired marine lieutenant general Michael DeLong, who was deputy commander of the Central Command as the US military prepared to invade Iraq in March 2003.
"When you walk into him you've got to be prepared. You've got to know what you're talking about. If you don't, you're summarily dismissed. That's the way it is," Lt Gen DeLong told CNN.
Mr Ruff said Mr Rumsfeld was focused on his work, not on the controversy. "This has not been a distraction to him," he told reporters. The secretary's view is people have a right to express their own opinion," he said.
"I'm not aware that we're doing anything different. We're coming to work and we're getting a lot of things done."
Mr Rumsfeld, who has had prickly relations with the military and Congress almost from the start of his first term in 2001, has survived prior calls for his resignation.
He offered Mr Bush his resignation after the Abu Ghraib prison abuse scandal in 2004, but the president turned it down.
Top Democrats, including Senator John Kerry, Democratic contender at the last presidential election, have joined recent calls for a change of Pentagon leadership.
General discontent
The latest military challenge comes from retired generals with direct experience of the Iraq war.
They also include retired major general John Batiste, who led the 1st Infantry Division in Iraq; retired major general Paul Eaton, who led initial efforts to train Iraqi security forces; and retired general Anthony Zinni, a longtime critic of the Iraq war and former head of Central Command.
Lt Gen Newbold, recalling the silence of senior military officials during the Vietnam War, has urged active duty officers to speak up. But Lt Gen DeLong again said the US system works.
"I mean we have civilian control of the military," Lt Gen DeLong said. "It's a good thing. And secretary Rumsfeld takes it literally. And that's a good thing. That's his style."
The calls by the retired generals represent a difficult political challenge for the administration in the middle of a war and also a blow to civil-military relations, analysts said.
Richard Kohn, a military historian at the University of North Carolina, said the problem runs deeper than just the disaffection of a few retired generals.
"It is serious, very serious in the growing civil-military tension of this administration, which has been considerable from the very beginning," he said
Mr Kohn said the confrontation threatens to poison relations between the military and civilian leaders, influencing not only their choice of whom to promote but also the candor of their interactions. Where it's going to go I do not know, but I think it ought to stop."