If I may say so, I think the conventional formulation about "cutting off" funding for the war in Iraq is a little misleading. The embedded presumption seems to be that there is a continuing and infinite stream of war funding that continues to flow until either the president removes the troops or else the congress cuts the stream. The federal government does not, however, actually operate in this manner. Rather, appropriations are made providing finite quantities of funds for specific purposes, sometimes with the purpose including an intention to delegate some discretion to the executive branch.
There are some ins and outs, but the point is this the default path is for the government to run out of money. Absent additional appropriations by the congress, the war money will simply be spent and none will be left. Nobody needs to "cut the funding" -- all that happens, in legal/budgetary terms, is that no additional money is appropriated. In practice, obviously, it's not going to come to that -- even during the 1995 "government shutdown" they made sure military forces deployed abroad had money. The point, though, is that this is where the budgetary rubber hits the policy road. Bush has a policy he wants to implement. Sooner or later, he needs to come to congress asking for money. What you're going to want to see is a resolution that says, "of course we'll appropriate money for the war -- here's $X billion to pay for a withdrawal plan scheduled to end by Date Y after which no more of this money will be spent." Bush is going to want to argue that he should veto this bill and that anything other than an unadorned appropriation of money to be spent as he sees fits constitutes an abandonment of our troops in the field. Liberals are going to want to argue the reverse -- that failure to sign the appropriation with the withdrawal proviso constitutes abandonment of the troops in the field.