WASHINGTON (CNN) -- The leaders of both houses of Congress criticized President Bush for threatening to veto bills that would set a deadline for withdrawing troops from Iraq.

"It's obvious from his statements following yesterday's vote here in the Senate that he doesn't want anything other than a confrontation," said Senate Majority Leader Harry Reid. "We want the Senate and the House to be a separate, independent branch of the government."

Reid and House Speaker Nancy Pelosi sent a letter to the President encouraging him to work with Congress. The legislation they back, which includes billions of dollars in war spending, also has provisions to set a deadline for withdrawing U.S. troops from Iraq.

"Given the importance and urgency of this legislation to our troops and our security, we are quite disturbed by your insistence to veto it," they said in the letter. "Rather than work with the Congress to develop a bill you could sign, you apparently intend to follow a political strategy that would needlessly delay funding for our troops."