At the center of a growing controversy, US Defense Secretary Donald Rumsfeld dashed hopes of a quick victory, saying Sunday that "the most dangerous and difficult days are still ahead of us."

But he nonetheless insisted allied victory was assured.

Finding that air strikes on Baghdad have not brought a swift end to Saddam Hussein's regime and instead inflamed Arab opinion, several former US generals blasted Rumsfeld for allegedly ignoring military brass advice and going to war with insufficient forces.

According to his critics -- including a 1991 Gulf War veteran, retired General Barry McCaffrey -- Rumsfeld likes hi-tech weapons and commando action, and did not deploy forces strong enough to swiftly take Baghdad and maintain the lengthy supply lines safe.

General William Wallace, commander of US ground forces in Iraq, said that the Americans had perhaps underestimated Iraqi resistance, especially in guerrilla-type fighting that has taken some toll on allied troops.

Wallace told The Washington Post in an interview published Friday that bad weather and unexpected Iraqi tactics would likely draw out the war. However, he denied there had been excessive US optimism in the build-up to war.

Wallace said that Vice President Dick Cheney had spoken in television interviews "about the risk of complications."

"He said 'weeks, not months'. He talked about how we don't know what the outcome can possibly be," Wallace said, in the administration's defence.

The Pentagon, which now has 90,000 troops in Iraq, will have another 120,000 troops already mobilized to join up with some 300,000 US and British soldiers in the region -- although not immediately.

Those soldiers include the 4th Infantry Division, equipped with heavy armor, which was to enter northern Iraq through Turkey. Turkey, however, denied permission, and those soldiers and their equipment will now enter Iraq from the south through Kuwait.

In the meantime, Washington this weekend orchestrated a counter-operation to try and win some terrain in the propaganda war.

General Tommy Franks, chief of operations, defended the "remarkable" way the war has progressed so far, with allied troops now less than 100 kilometers (60 miles) from Baghdad on several fronts.

And Franks denied there was any differences with Rumsfeld. "No one has driven the timing of this operation except the operational commander," he said from his computerized command headquarters in Qatar.

Franks spelled out the successes so far in 11 days of warfare, with oil fields in the south secured, allied forces in control of the skies, the destruction of a terrorist base in the north, control of the coastline, and the opening of a northern front.

Irritated by scathing comments from an impatient US press, Rumsfeld on Sunday rejected "second-guessers" and their criticism.

Franks' strategy is "excellent" and being followed minutely, Rumsfeld said, adding that the United States had never had a timetable for victory.

Meanwhile US military officials refused to confirm there has been a "pause" in US-led operations in central Iraq, journalists on the scene reported.

"There is no pause in action across the whole battlefield," said Pentagon spokesman David Lapan. "There are movements from west, south, from north, so there are lots of movement misperceptions of the big picture."

WAR.WIRE