The prospect of a partial government shutdown increased significantly this morning.

President Barack Obama made it emphatically clear that he is not in any way open to negotiating a delay or a weakening of his health care law. He spoke just minutes after House GOP leaders announced plans to pass legislation this week that would make defunding Obamacare their condition for stopgap spending until December and an increase in the debt limit good for at least a year.

The president, in remarks to corporate executives at the Business Roundtable, said he won’t allow a “faction” of the most conservative Republicans to “extort” such a concession from him because that “would fundamentally change how American government functions.”

“We will blow the whole thing up unless you do what we want? That can’t be our recipe for governing,” he said in characterizing the Republican plan. He also contended that this could jeopardize the economic recovery by rattling financial markets close to the next two budget deadlines — the start of the fiscal year in a dozen days and the Treasury’s need to borrow money beyond the legal limit sometime in the middle of October.

The remarks were perhaps the president’s most succinct and confrontational yet in this fall’s intensifying version of the budget wars that have consumed so much of Washington’s energies for the past three years. He is hoping to win the battle for public perception the same way Bill Clinton did during a series of shutdowns at the end of 1995. Republicans then were overwhelmingly viewed as petulant and blamed for allowing federal services to grind to a halt because they didn’t get their way in negotiations over cuts in social programs.

Speaker John A. Boehner, who was on a lower rung of the GOP leadership ladder back then, remembers the political beating his side took and has been openly resistant to tactics that could lead to a repeat performance. But the Ohio Republican was quickly overruled at a closed-door meeting of his caucus this morning, and he and Majority Leader Eric Cantor emerged to explain that their latest strategy in the budget battle is to tie straightforward spending and debt provisions to at least two poison pills — provisions to prevent any spending to implement the health care law, which is to take a major step in October with the opening of insurance exchanges, and a requirement that Obama allow construction of the Keystone XL oil pipeline, which he has remained ambivalent about for two years.

There is no way the Democratic Senate would approve legislation defunding Obamacare, no matter its other provisions,. And the odds the Keystone language would survive look only slightly better.

There were some indications in Boehner’s remarks that he might countenance a strategy, only slightly different from the one he was forced to abandon last week, in which the Senate would strip out the provisions it found objectionable and send back to the House a relatively clean measure with the two fiscal provisions — continuing discretionary spending until Dec. 15 at the current sequester-clipped levels (an annualized rate of $988 billion), and permitting the Treasury to borrow whatever it deems necessary through next fall, and presumably beyond the midterm elections.

If the Senate at least goes on the record with a roll call sticking up for Obamacare — such a vote has never happened, even as the House has voted 40 times to defang or repeal the law — the leadership’s hope would be that a sufficient bloc of House conservatives would feel they had done the best they could to promote their cause, relent and allow the budget crisis to be avoided in the nick of time.

At least for today, though, the atmospherics on both sides suggest that a government shutdown lasting at least a few days might be required to focus the negotiators’ minds.