Increased violence in Iraq (search) is pushing the cost of the war over budget, possibly by as much as $4 billion by late summer, the top U.S. military officer said Wednesday. And billions more will be needed for the rest of the year.

Gen. Richard Myers (search), chairman of the Joint Chiefs of Staff, said the recent decision to extend the stay of some 20,000 troops will cost roughly $700 million more over three months. The White House is keeping open the possibility it will seek additional funds before the end of this election year.

"When the service chiefs last talked about this, there was, I think, a $4 billion shortfall," Myers told the House Armed Services Committee. "We thought we could get through all of August. We'd have to figure out how to do September."

The war is costing an estimated $4.7 billion a month, officials said. Defense officials are studying their current budget, which runs through Sept. 30, to determine whether some money can be moved from purchase programs or other Pentagon accounts, Myers said.

Lawmakers expect to have a defense bill in place by the time the new budget year begins Oct. 1. But the version President Bush proposed had no money for U.S. operations in Iraq and Afghanistan (search). Nevertheless, legislators say the Pentagon could use money from that bill until extra money for the war is provided.

White House officials have already said they would propose a separate bill after this fall's elections — costing up to $50 billion — to pay for the two wars.

But Wednesday, presidential spokesman Scott McClellan said the final decision on what was needed — and when — would be "based on what the commanders in the field feel is necessary." McClellan said Pentagon officials have assured the White House they have the money they need.

On a day when nearly 70 people were killed by suicide bombers in Iraq's southern city of Basra, Myers and Deputy Defense Secretary Paul Wolfowitz testified for a second day on Capitol Hill. American troops this month have endured the worst casualties of the year-old campaign, with 100 killed.

At the hearings this week, lawmakers also have asked what the Pentagon would do if more troops are needed; Myers said the military is working up a plan for who could go. Lawmakers hoped more foreign troops might come to Iraq, but Wolfowitz said not many would while the violence continues.

Some lawmakers complained the Bush administration consistently has denied them information about Iraq over past 18 months.

Because of increased costs, Rep. Duncan Hunter, R-Calif., chairman of the House Armed Services Committee, said he plans to add $20 billion for the current budget year to the 2005 defense bill now being considered.

Several lawmakers complained anew that the administration's 2005 budget request for the Defense Department was sent to them with no money in it for Afghanistan or Iraq.

Administration officials have acknowledged they will need $50 billion for those wars. But the officials said they would not ask for it until after January — and after the presidential election in November.

"The administration would be well served here to come forward now, be honest about this, because the continuity and the confidence in this policy is going to be required to sustain it," Sen. Chuck Hagel, R-Neb., said in a television interview. "And that means be honest with the Congress, be honest with the American people."

"They are simply trying to conceal the cost of this operation until after the election," said Rep. David Obey of Wisconsin, top Democrat on the House Appropriations Committee.

Republican lawmakers planned to meet on Thursday with national security adviser Condoleezza Rice in the Capitol for an update on developments in Iraq.