With a government shutdown looming and budget talks apparently at a standstill, Democratic aides are accusing the GOP of moving the goalposts for compromise yet again.

A senior Senate Democratic aide tells me that in today’s private meeting at the White House, Speaker John Boehner signaled to the President and to Harry Reid that Republicans were not willing to support any budget compromise that can’t garner the votes of 218 Republicans in the House. That would be a break from the GOP’s previous posture: Republican leaders had appeared willing to reach a deal that could pass the House with Republican and Democratic support, even if it meant losing some Republicans.

Harry Reid is expected to make an accusation along these lines today when he speaks to the press, the aide tells me, though this could change, depending on fast-shifting circumstances.

“Our takeaway from the meeting was that Republicans will not accept anything that cannot pass the House without 218 Republican votes,” the aide tells me. “That means $73 billion isn’t good enough.”

That last line means that the $33 billion in cuts as a proposed target compromise — on top of $40 billion of cuts that were already agreed upon — will not be sufficient for a compromise, if 218 Republicans cannot support it.

If Reid’s takeaway from the meeting is accurate — the GOP’s readout of the meeting did not indicate this version of events, and a Boehner spokesman didn’t immediately return an email for comment — it would mean that House GOP leaders have decided they are not willing to back a compromise if it means sacrificing significant Republican support on their right flank .

“Rather than finding common ground, they’re more concerned with appeasing the Tea party and extreme right wing than finding common ground with Democrats,” the Dem aide continued.

In a surprise appearance before the White House press corps moments ago, Obama didn’t divulge what happened at the meeting. But he did point out that Republicans appear to be rejecting the current compromise number of $73 billion, even though that is the original number articulated by Boehner, before conservatives began demanding deeper cuts.

“We are now at the figure that was Speaker Boehner’s original proposal,” Obama said. “Speaker Boehner originally called for $73 billion worth of cuts. Members of his caucus insisted on making it $100 billion. What we’ve said is, `We’re willing to go to 73.’”

More when I learn it...

UPDATE: A House GOP aide, asked for comment, did not deny the above account, saying only: “Given that Sen. Reid hasn’t yet managed to pass a long-term CR through the Senate, while Speaker Boehner has passed on in the House, he should probably stick to his own knitting.”

UPDATE II: Harry Reid, speaking to reporters just now, went public with this charge, claiming: