Passage of the legislation capped a four-month struggle between President George W. Bush and the new Democratic-led Congress over the increasingly unpopular Iraq war, now in its fifth year.

Three Democratic senators running for president, Hillary Rodham Clinton of New York, Barack Obama of Illinois and Christopher Dodd of Connecticut, opposed providing money with no withdrawal deadlines.

With this latest installment, the United States will have allocated more than US$565 billion for the wars in Iraq and Afghanistan since 2001, according to the Congressional Research Service. Most of the money has gone to fight in Iraq.

Mr Bush pleaded for patience but warned of more tough times ahead. "It could be a bloody, it could be a very difficult August," he told reporters at the White House.

But he also made clear September will be an important period, when the US commander in Iraq, Gen. David Petraeus, will report on the impact of the troop buildup and make a recommendation on how to proceed.