"The conventional wisdom is the US mistake in Iraq was not enough troops," said Thomas Blanton, the archive's director. "But the Desert Crossing war game in 1999 suggests we would have ended up with a failed state even with 400,000 troops." About 144,000 US troops are now in Iraq, down from a peak of about 160,000 in January.

The war games looked at "worst case" and "most likely" scenarios after a war that removed Saddam Hussein from power. Some are similar to what occurred after the US-led invasion of Iraq in 2003. "A change in regimes does not guarantee stability," the 1999 seminar briefings said. "A number of factors including aggressive neighbours, fragmentation along religious and/or ethnic lines, and chaos created by rival forces bidding for power could adversely affect regional stability." The papers said the replacement regime could be problematic - especially if perceived as weak, a puppet, or out of step with regional governments.

"Iran's anti-Americanism could be inflamed by a US-led intervention in Iraq," the briefings read. "The influx of US and other western forces into Iraq would exacerbate worries in Tehran, as would the installation of a pro-western government in Baghdad." The briefings also revealed that some participants believed that "no Arab government will welcome the kind of lengthy US presence that would be required to install and sustain a democratic government", and that a military intervention may be at odds with many coalition partners.

In Iraq on Saturday seven parents of US servicemen flew into the northern town of Irbil at the start of a seven-day visit to the place where their children had been killed. No US troops are stationed in Irbil now but during their visit the seven hope to meet troops, Iraqis and government leaders, said the organiser, Move America Forward. "No other such co-ordinated trip to Iraq by families of fallen troops has ever taken place," said the California-based group, pro-troop organisation founded in 2004. The group's chairwoman, Melanie Morgan, said: "We felt it was time to allow the families of US troops who died in Iraq to see the progress being made in Iraq."

Associated Press, Reuters