Arriving on Thursday in Baghdad against a backdrop of increasing assaults on US-led forces, Rumsfeld claimed things have been looking up in Iraq since major combat was declared over on 1 May.
"There has been measurable progress," Rumsfeld said after meeting US occupation administrator Paul Bremer and Lieutenant General Ricardo Sanchez, the top US military commander in Iraq.
"It is getting better every day," he added.
The defence secretary cited as an example of improvement the fact that the number of Iraqi security forces, including police, border guards, militia and army had grown to 55,000. The number could rise to 100,000 in the future, he added.
Rumsfeld said Sanchez had not asked for additional US troops for Iraq. "If he wanted more troops, he would have them," he said.
Rumsfeld did his best to dispel impressions that Iraq has been slipping into anarchy.
Rumsfeld insists life for Iraqis
is improving under US occupation
"It is understandable that with so much analysis and so much observation and so much scrutiny as to what's going on here that the emphasis tends to be on the things that are unfortunate ... where somebody is killed, or somebody is wounded, or some building is blown up, or someone is critical of the governing council or critical of the coalition," he explained to journalists.
"It tends to create an impression, an imbalance in public perception that is unfortunate," he added.
Immediately after landing at Baghdad, he visited US soldiers, some of whom were wounded this week by resistance fighters who appear to be growing in numbers in Iraq.
"It is getting better every day"
Donald Rumsfeld, US Defence Secretary
But an unflappable Rumsfeld maintained the number of attacks were leveling off from nearly 13 attacks daily, and there were signs of improvement.
"Its been fairly level in recent weeks," he said after arriving for the first leg of a previously unannounced whirlwind tour.
Rumsfeld aides said his trip was shrouded in secrecy before his arrival to Baghdad for security reasons.