BAGHDAD, June 16 U.S. forces have begun a major offensive against al-Qaida in Iraq, the U.S. commander in Iraq said Saturday.Gen. David Petraeus, speaking at a news conference in Baghdad with U.S. Secretary of Defense Robert Gates, said the offensive is designed to take the fight to al-Qaida and cut into the organization's ability to carry out its car-bombing campaign, The New York Times reported.The operation comes as U.S. officials confirm the surge of U.S. combat troops into the region has been completed.It also comes at what the newspaper called a critical time in the Iraq war, with increasing U.S. casualties and growing political pressure in the United States for either more progress in Iraq or a U.S. troop withdrawal.Petraeus is to report to President George Bush in September on the results of the troop surge the president ordered at the beginning of 2007.The new offensive, targeted at insurgent cells and bomb-making facilities outside Baghdad, is expected to be sustained and involve tough fighting, the Times said.Copyright 2007 by UPI