Franks, speaking at a daily briefing of the U.S. Central Command in Doha, Qatar, was responding to published reports that the requests of U.S. generals for more ground troops were repeatedly denied by Rumsfeld. Reports also quoted U.S. military officials as saying the lack of troops and weapons meant the war might last into the summer.
"One never knows how long a war will take," Franks said.
For his part, Rumsfeld said the plan was all Franks' idea and called it "innovative."
Like Franks, Rumsfeld did not put forth a timetable for the war's end.
"We've never had a timetable. We've always said it could days, weeks or months and we don't know. And I don't think you need a timetable," Rumsfeld said in a broadcast interview.
He acknowledged that resistance "has been in pockets quite stiff. It's going to get more difficult as we move closer to Baghdad," where President Saddam Hussein's most trusted and battled-tested Republican Guards are waiting.
The Washington Post reported that current and former U.S. military officers are blaming Rumsfeld and his aides for the inadequate troop strength on the ground in Iraq, saying the civilian leaders "micromanaged" the deployment plan out of mistrust of the generals and an attempt to prove their own theory that a light, maneuverable force could handily defeat Iraqi President Saddam Hussein.
More than a dozen officers interviewed, including a senior officer in Iraq, said Rumsfeld took significant risks by leaving key units in the United States and Germany at the start of the war. That resulted in an invasion force that is too small, strung out, underprotected, undersupplied and awaiting tens of thousands of reinforcements who will not get there for weeks.
But despite complications from Saddam's arming of paramilitary groups, his preparations for street warfare in Baghdad and in other cities and Iraqi soldiers' fake surrenders, Pentagon defense leaders remained confident about the pace of the invasion. They said the deployment of 100,000 additional forces to Iraq was planned months ago.
U.S. and British forces topped 290,000 in the Persian Gulf. The Army's 4th Infantry Division was being sent, its first supplies expected to arrive in Kuwait within days, and armored cavalry troops and gun-mounted Humvee utility vehicles could be deployed sooner than scheduled.
Franks started his briefing by rattling off nine successes of coalition forces since the beginning of the war, starting with securing southern oil fields.
"The Air Force has worked 24 hours a day across every square foot of Iraq, and every day the regime loses more of its military capability," Franks said.
Obviously responding to growing public questions about the U.S. preparation for the war in light of strong resistance met by forces in south and central Iraq, Franks appeared angry at the start of the briefing.
"We're in fact on plan. And where we stand today is not, in my view, only acceptable, but truly remarkable," he said.
Franks also rejected reports that his forces had engaged in an "operational pause" near the gates of Baghdad. U.S. ground forces are about 50 miles south of the city.
"There have been some pundits who have indicated we may be in an operational pause," Franks said. "This simply is not the case."
CBS News Analyst Gen. (Ret.) Perry Smith, for one, feels the capture of Baghdad will present many challenges, but he's not convinced it will be a lengthy campaign.
" … the battle is not likely to take very long, cause many civilian casualties, or many casualties on the part of coalition forces," Smith said
"Fortunately, America and its coalition partners enjoy many advantages that should make the fall of Baghdad less difficult than many pundits and experts predict."
On other fronts, Franks said the coalition had achieved air and ground freedom of action in western Iraq, was staging air operations from a number of captured air fields and had secured the coastline, clearing the way for humanitarian aid shipments to begin.
He said coalition forces had also destroyed a massive terrorist facility in northern Iraq. At least 120 militants were killed in the attack on Ansar al-Islam, an extremist group suspected of being linked to the al Qaeda network.
He also said Iraqis opposed to Saddam were working with coalition forces, notably in an-Nasariyah, where they provided records on ruling Baath party officials. He did not elaborate.
Warplanes have dropped some 6,000 precision-guided munitions, Pentagon officials said, and 675 Tomahawk cruise missiles have been launched from the air and sea -- just seven missing their targets because of apparent mechanical malfunctions.
Tomahawk launches from the eastern Mediterranean Sea and the Red Sea were temporarily suspended because some missiles fell into Turkey and Saudi Arabia on their way to Iraq.