Heavy pressure from Senate Republicans and conservative advocacy groups that want to defund Obamacare on Wednesday helped kill a House bill that would have averted a government shutdown.

House Majority Leader Eric Cantor, R-Va., on Wednesday suddenly cancelled a Thursday vote on a stopgap funding bill that would have funded the government beyond the Sept. 30 expiration of the current fiscal year, through Dec. 15.

Republican leaders were unable to round up the 217 votes need to pass the House after intense lobbying efforts by Senate Republicans and outside groups. Fourteen senators signed onto a bill calling for all Obamacare funding in the temporary budget bill to be eliminated.

"We put on pretty heavy pressure to get the House members to understand," a Senate GOP aide told the Washington Examiner.

The House bill, introduced by Cantor on Tuesday, did not actually defund Obamacare. Instead, Cantor sought to appease conservative Tea Party lawmakers with an measure that would have forced the Senate to vote separately on whether to defund the health care law.

Some House conservative immediately dismissed Cantor's plan as a gimmick, but others were swayed, in part because Republicans are eager to dodge the political blame for shutting down the government.

"So we talked to enough people to make sure they understood that this is probably the worst thing to do because it gives cover to vulnerable Democrats on the defunding side of this," the Senate aide said.

Republicans hope to take control of the Senate in the 2014 elections and could do so by defeating Democrats up for re-election in swing districts.

Outside groups like the Conservative Action Project also have been pressuring lawmakers to reject Cantor's proposal and seek a full defunding of the health care law.

The Conservative Action Project called the GOP leadership's plan, "a procedural gimmick designed to give the appearance that Obamacare is not being funded, while giving the Senate the ability to easily fully restore funding for Obamacare."

Lawmakers, the aide said, were warned by the outside groups that if they voted for Cantor's bill, "we will let everybody know what we think about this in a very aggressive way."

An aide to Cantor told the Examiner that the vote on the budget bill will be postponed until next week, but was on course to pass.

"We’re still having conversations with members and making progress," the aide said. "Since it was just announced yesterday, getting anything this big accomplished in 72 hours is always tough and we just need a couple of extra days."

The fight to use the temporary spending bill as a means of defunding Obamacare could become one of the toughest political dilemmas the GOP leadership has faced.

Republicans will have to find agreement within their conference, because Democrats have no intention of helping them pass the budget bill that would cut $986 billion, which is only slightly lower than sequester levels.

Democrats, however, want to restore funding cut by the sequester.

When the budget bill was pulled in the House Wednesday, Democrats pounced on the chance to highlight the GOP infighting.

“The American people are witnessing yet another sign that Republicans can’t get their own act together, even when a government shutdown hangs in the balance," House Minority Leader Nancy Pelosi, D-Calif., said.