Former President Donald Trump on Tuesday said congressional Republicans should pursue a government shutdown if they cannot attach a hardline voting bill to the temporary funding resolution that would keep the government open.

"If Republicans in the House, and Senate, don't get absolute assurances on Election Security, THEY SHOULD, IN NO WAY, SHAPE, OR FORM, GO FORWARD WITH A CONTINUING RESOLUTION ON THE BUDGET," the Republican presidential nominee wrote in a Truth Social post.

"THE DEMOCRATS ARE TRYING TO 'STUFF' VOTER REGISTRATIONS WITH ILLEGAL ALIENS. DON'T LET IT HAPPEN – CLOSE IT DOWN!!!"

House Speaker Mike Johnson, R-La., is currently trying to pass a six-month stopgap funding bill paired with the controversial SAVE Act, a legislative proposal that would require individuals to show proof of citizenship at the ballot box.

Congressional Democrats have repeatedly signaled they will not pass a funding bill attached to such a policy, which they see as a "poison pill," or a controversial bill tied to a piece of legislation as a way to tank the overall deal.

"The House Republican CR is an unserious and uncooked product," Senate Majority Leader Chuck Schumer, D-N.Y., said on the Senate floor Tuesday. "Republicans should work with Democrats on a bipartisan package, one that has input from both sides, one that avoids harmful cuts, one that is free of poison pills."

Congress has until Sept. 30 to strike a funding deal or else risk triggering a partial government shut down.

As that deadline inches closer, Johnson has showed no signs of backing down from the SAVE Act bill attachment, staying in line with Trump's wishes even as Democrats remain firm on their pledge to vote against it.

As Democrats and Republicans approach a deadlock, Senate Minority Leader Mitch McConnell, R-Ky., is willing to break with hardliners who insist the party must preserve the SAVE Act, even at the cost of a government shutdown.

"Shutting down the government is always a bad idea," McConnell said Tuesday.

That same day, the House approved the rule for the CR, which would fund the government until March 2025, with the SAVE Act included.

The final House vote to pass the funding bill is set to take place Wednesday. But even if it passes, the bill would still be dead on arrival in the Democratic-controlled Senate.

— NBC News' Sahil Kapur contributed to this report.