By Richard Cowan

WASHINGTON (Reuters) - Democratic leaders in the House of Representatives said on Tuesday that they will try to pass a new Iraq war-funding bill to keep combat operations running for the next two or three months while also forcing a troop withdrawal vote in July.

House Majority Leader Steny Hoyer, a Maryland Democrat, said a vote could come as early as Thursday on a new plan to provide more than $30 billion (15 billion pounds) now for combat operations in Iraq and Afghanistan before existing war funds run out. Another $10 billion or so would beef up veterans health care and other military programs.

The House vote would come in the midst of a three-month fight between congressional Democrats and the White House over the Iraq war and as the Pentagon adds 30,000 U.S. troops to help secure Baghdad from sectarian violence that has spiralled out of control.

Last week, Bush vetoed a $124 billion war funding bill because it called for a phased withdrawal of combat troops starting no later than October 1.

House Appropriations Committee Chairman David Obey, a Wisconsin Democrat, said the bill he and Democratic Representative John Murtha of Pennsylvania have drafted would give Bush "two more months to demonstrate there was a prayer his plan can succeed."

In the meantime, Bush would have to deliver to Congress by July 13 progress reports about Iraqi military units in taking over operations from U.S. forces, along with reports on Iraq's progress in passing an oil revenue distribution law and other measures to create domestic political stability.

Under the Obey-Murtha plan, which is still being mulled by Democrats, Congress would have about 10 days to review Bush's reports.

Then, in late July, Congress would be faced with a decision: Whether to dedicate the next batch of emergency military funds, around $50 billion, to continue combat or to use the money to bring the combat troops out of Iraq.