WASHINGTON (AFP) - The withdrawal of marines from Fallujah is "an opportunity, not necessarily an agreement" to end fighting for the city, the commander of US forces in Iraq (news - web sites) said, warning that military action may still be needed to root out foreign fighters. General John Abizaid said the United States will not tolerate foreign fighters in the city, and will insist on heavy weapons coming off the streets and on freedom of movement for marines and Iraqi security forces. He said it should be understood that "what we have there is an opportunity, and not necessarily...