"I anticipate we'll be involved in Iraq in the future," Tommy Franks, a former head of the US Central Command, told the House Armed Services Committee Thursday. "Whether that means two years or four years, I don't know."

He said it would be unwise to raise expectation that "difficulties" faced by coalition forces in the country "will go away in one month or two months or three months."

The number of US soldiers killed in hostile action in Iraq since May 1, when President George W. Bush declared an end to major combat operations, has reached 31 as troops continued to hunt down Saddam Hussein loyalists.

Franks also expressed confidence in the reliability of US intelligence, and insisted weapons of mass destruction would be found.

He said there were roughly 1,000 suspect sites to comb through where weapons of mass destruction might be stashed.

"That work is not completed. And so I believe that we will either find the weapons or we will find evidence of the weapons of mass destruction," Franks said.

US military top brass were all convinced of the accuracy of intelligence concerning Saddam's arsenal and the certainty of the threat posed by such weapons before and during the war, he said.

When asked whether the White House had overstated the risk posed by the ousted Iraqi president, Franks answered: "I do not believe that at all."

Military officials donned protective gear on numerous occasions during the war, and ordered troops to do the same, after US intelligence strongly indicated that a chemical attack was imminent, Franks said.

Franks' vote of confidence in US security did little to check calls by opposition Democrats for a full-scale investigation into US intelligence lapses leading up to the war.

One leading Democrat and presidential candidate, Massachusetts Senator John Kerry, on Thursday lent his voice to the growing chorus of lawmakers calling for a thorough congressional probe.

"This is a national security issue for our country," he said at a press conference.

"The quality of our intelligence is critical, not just to the judgments that Congress makes but to our credibility in the world and to the capacity of the president to reach out to other countries and build the kind of coalitions we need to win the war on terror."

"I believe we need an open, thorough, complete and absolutely believable investigation into the quality of American intelligence so that going forward from now the national security interests of our country will be properly protected," said the senator, who is one of nine Democrats vying for the party's presidential nomination next year.

Democrats' calls for more muscular congressional investigations into US intelligence followed White House revelations earlier this week that it relied on bogus information in making earlier claims that Iraq had tried to obtain nuclear materials from Africa.

In the South African capital Pretoria this week, US President George W. Bush maintained that even if isolated pieces of intelligence were flawed, the overall mission to overthrow Saddam was correct and just.

"There is no doubt in my mind that Saddam Hussein was a threat to the world peace and there is no doubt in my mind the United States along with our allies and friends did the right thing in removing him from power," Bush said.

Meanwhile, Secretary of State Colin Powell at a press conference Thursday called the charges of hyped intelligence "overwrought and overblown and overdrawn."

"Intelligence reports flow in from all over.... Sometimes it holds up, sometimes it does not hold up," he said.

"It's a moving train, and you keep trying to establish what is right and what is wrong," said Powell.

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