The House Freedom Caucus sent a letter Wednesday to Senate Minority Leader Mitch McConnell, R-Ky., urging him to use "all procedural tools" at his disposal to delay a stopgap measure to extend government funding into January unless Democrats agree to prohibit funding for President Biden’s COVID-19 vaccine mandate.

Lawmakers are rushing to approve a short-term spending bill, known as a continuing resolution (CR), ahead of Friday’s deadline to briefly extend the deadline to January and avoid a government shutdown. Republicans are hoping to block its passage or at least delay it past the midnight deadline Friday unless Democratic leaders agree to strip out funding to enforce the mandate.

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Senate Minority Leader Mitch McConnell

Senate Minority Leader Mitch McConnell walks to the Senate Chamber on Capitol Hill on Nov. 3, 2021 in Washington. (Joshua Roberts/Getty Images)

"Today the House of Representatives will pass, over our objection, a continuing resolution to fund government without ending any of President Biden’s very damaging, unAmerican, and in the worst cases, unlawful vaccine mandates," the caucus, chaired by Rep. Scott Perry, R-Pa., wrote in its letter.

"As you know, the current government funding mechanism expires on Friday night, thus the Senate Republican conference enjoys important leverage against those mandates," it continued. "We therefore write to request that you use all procedural tools at your disposal to deny timely passage of the CR unless it prohibits funding – in all respects – for the vaccine mandates and enforcement thereof."

Sen. Patrick Leahy, D-Vt., who chairs the Senate Committee on Appropriations, said he’s confident Republicans won’t follow through on their threat.

"I don’t think Republicans want to be involved in shutting down the government," he told Fox News on Wednesday. "They've done that before [and] it backfired."

Sen. Patrick Leahy (D-VT)

Sen. Patrick Leahy speaks with reporters on Nov. 30, 2021 in Washington. (Kent Nishimura/Los Angeles Times via Getty Images)

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McConnell said Tuesday that he didn't foresee a shutdown.

"We won't shut down," he told reporters. "I think we'll get there and certainly nobody should be concerned about a government shutdown."