A former US national security adviser who served in the administration of the first president Bush, warned on Saturday that the war in Iraq threatens to grind on for years like the Vietnam conflict.
"It could become a Vietnam in a way that the Vietnam war never did," Brent Scowcroft said in a an interview published in Portuguese weekly newspaper Expresso.
"Our exit from that country did not have grave consequences while if we wanted to get out of Iraq today, the consequences would be very deep."
Scowcroft, who led a classified review of US intelligence in 2001 and heads the Foreign Intelligence Advisory Board of the current President George W. Bush, was an outspoken critic of the US-led invasion of Iraq, arguing it took the focus off the fight against the extremist al Qaeda network.
He told the newspaper he believed the neo-conservatives who strongly backed the invasion did not realise how difficult it would be to foster a democratic system in Iraq once the regime of Saddam Hussein was toppled.
"Their plans are fantastic but very difficult to apply because it is very difficult to implant deep political alterations in a society," he said.
"This is the problem we are facing in Iraq and we do not have a magic wand to create a democratic society, or create a group of people who aspire to democracy."
Snowcroft added he believed the current Bush administration has stopped hinting at the possibility of military intervention in other nations, like Syria and Iran, because Washington is disappointed with the results it obtained in Iraq.
Major fighting dragged on for eight years in Vietnam, from 1965 to 1973. More than three million US troops served in the conflict, and more than 58,000 Americans were killed.
Bush administration officials have bristled at any comparisons between the war in Vietnam and the conflict in Iraq, which began last March.
Before launching the invasion Bush argued that US officials erred in Vietnam because "we could not explain the mission, had no exit strategy and did not seem to be fighting to win."
But while the Iraqi regime has been ousted and its army disbanded, US forces in the country continue to face regular attacks and Washington has not yet set a timetable for their withdrawal from the country.