I’m glad to see Bush pushing back on this. The House Democrats shouldn’t be allowed to hold the troops hostage while they try to figure out a way to make their base happy. Either they defund the war outright or not at all. No tricky, underhanded defunding techniques should be allowed:

President Bush would veto a bill drafted by House Democratic leaders that would fund the Iraq war only into the summer months, his spokesman said Wednesday.
The Democrats’ proposal would pay for the war through July, then give Congress the option of cutting off money after that if conditions do not improve. Bush requested more than $90 billion to fund the war through September.
[…]
Asked directly if Bush would veto the House bill in its current form, Snow said, “Yes.”
[…]
The new proposal is aimed at appeasing Democratic lawmakers who want to end the war immediately and are urging leaders not to back down after Bush’s veto. But lacking a firm endorsement by the Senate, the challenge by House Democrats seemed more for political show than a preview of another veto showdown with Bush.

There are a couple senators from red states who are up for re-election, I don’t think they want to run against ads that show them voting to cut funds in July when the military says that it will take until September to get an assessment of the success of the surge.
BTW, do they really want to pull the troops when even Clinton is saying that there has been some success?

Asked yesterday during a Town Hall-style event in Red Oak, Iowa about what to do about Iraq, Hillary Clinton made the familiar argument that the troops needed to be extricated from a civil war. But she also added some notably optimistic comments about the soldiers’ recent success in the mostly Sunni Al Anbar province where Al Qaeda has its stronghold.

“The war is 360 degrees, there is no battlefield,” she said. “So I want to get our combat troops out of a sectarian, civil war. And I have also said, and I somewhat do differ with some of my other colleagues, I think you have to take a hard look at the situation we are in. We are making some progress it turns out, in what is called Al Anbar province against al Qaeda, and the reason we are is that our military leaders have learned a lot in the last several years there and they have made common cause with some of the tribal leaders, who don’t like Al Qaeda any more than we do because Al Qaeda is also going after them.”