U.S. President George Bush accused Democrats in Congress of being irresponsible in their approval of war bills that set withdrawal dates for U.S. troops in Iraq.

Bush said the bills will backfire and may even end up keeping some troops in battle for longer than necessary.

"In a time of war, it's irresponsible for the Democratic leadership in Congress to delay for months on end while our troops in combat are waiting for the funds," Bush said in a Rose Garden news conference Tuesday.

"The bottom line is this: Congress' failure to fund our troops on the front lines will mean that some of our military families could wait longer for their loved ones to return from the front lines. Others could see their loved ones heading back to the war sooner than they need to."

Bush has been at odds with Congress since the Democrats took power in November, on the heels of widespread anti-war sentiment. Democrat leaders have promised to pressure Bush into bringing troops home early by keeping a tight grip on the Iraq funding purse strings.

But the president fought back, saying he'll veto two separate bills -- one passed in the Senate, the other in the House -- that call for most U.S. troops to exit Iraq no later than September 2008.

Bush reaffirmed that Congress could not override a veto of the bills which he said "undercut the troops."

Senate Majority Leader Harry Reid, a Democrat from Nevada, said Thursday that he would move to block money for the war if Bush rejected a proposal by Congress to set a deadline to end combat.

"It's interesting that Harry Reid, leader Reid, spoke out with a different option," Bush said. "Whatever option they choose, we hope they get home, get a bill, and get it to my desk."

"And if it has artificial timetables for withdrawal, or cuts off funding for our troops, or tells our generals how to run a war, I'll veto it."

The House and Senate are planning to send Bush a bill approving US$96 billion in new spending for Iraq. However, it will only be given if an end date for combat is set.

"If the president vetoes the supplemental appropriations bill and continues to resist changing course in Iraq, I will work to ensure this legislation receives a vote in the Senate in the next work period," Reid said in a statement before Bush's comments.

A spokesman for Reid told The Associated Press that the bill would cut off funds for the war but would probably be introduced as standalone legislation, instead of being tied to the supplemental spending bill.

If Reid proceeds with his proposal, it would be the strongest measure taken by the Democrats to pressure Bush on Iraq.

With files from The Associated Press