FALLUJA, Iraq (Reuters) - U.S. air strikes on Falluja and sharp skirmishes with guerrillas inside the besieged city Monday threw doubt on a deal U.S. officials had hoped might end one of their biggest problems in Iraq (news - web sites). At least 10 U.S. Marines were wounded, four seriously. In a rare reminder of the original trigger for last year's invasion, a Baghdad warehouse blew up during what seems to have been a raid by the force hunting Saddam Hussein (news - web sites)'s still elusive chemical and biological weapons. Four U.S. military vehicles were destroyed but the...