Negotiations on a spending accord needed to avert a government shutdown Friday have nearly collapsed, and Republicans say it’s because House Democrats are pushing for new limits on how many illegal immigrants agents from Immigration and Customs Enforcement can detain this fiscal year, including violent felons.

“Currently there is no cap,” a senior Republican aide close to the negotiations told the Washington Examiner. “They want to put in a cap and have criminals count against it so the number gets smaller and smaller.”

The impasse threatens to end any chance of a deal that can be passed in time by both the House and Senate.

“We would have to have something ready by tomorrow and at this point we won’t be ready,” a second GOP aide said.

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[Related: Richard Shelby on border deal: 'Talks are stalled right now']

A senior Democratic aide disputed the Republican position and said the vast majority of detainees are not felons. “What we are doing is trying to have a limit on the number of [detention] beds,” the Democratic aide told the Washington Examiner. “That’s about ensuring that the administration is prioritizing the deportation of violent criminals.”

Senate Appropriations Committee Chairman Richard Shelby, R-Ala., told "Fox News Sunday" the talks had stalled over Democrats demanding caps on ICE detentions. In order to detain illegal immigrants there must be a bed for them, and a cap on beds would limit the number of detentions.

The Democratic aide called Shelby’s morning talk show comments “an intentional lie.”

Rep. Lucille Roybal-Allard, D-Calif., a top appropriator and one of the negotiators, issued a statement defending the call for a cap on detentions.

"For far too long, the Trump administration has been tearing communities apart with its cruel immigration policies," Roybal-Allard said. "A cap on ICE detention beds will force the Trump administration to prioritize deportation for criminals and people who pose real security threats, not law-abiding immigrants who are contributing to our country."

The partisan tension escalated as staff for Republicans and Democrats over the weekend worked out the details of a deal that can be passed by Congress and sent to President Trump by Feb. 15, when a temporary spending bill runs out. In addition to staff talks, Shelby and House Appropriations Committee Chair Nita Lowey, D-Calif., have been negotiating directly this weekend.

The talks hit a wall when House Democrats on the negotiating team demanded the cap on the average daily population held in detention by ICE be capped at 16,500 individuals between enactment and the end of fiscal 2019, which ends on Sept. 30.

That provision was included in a proposal introduced by Lowey and fellow Democrats last month. According to that document, the cap aligns with the number of individuals ICE arrested and held in the last three months of the Obama administration.

Democratic negotiators are insisting the 16,500 number must include the thousands of illegal immigrant felons ICE arrests and detains as well, Republicans told the Washington Examiner. “That’s a nonstarter,” one of the two senior GOP aides said.

The aides said they believe the Democrats are pushing for the cap as “a nod” to the party’s “abolish ICE” faction, which includes freshman star Rep. Alexandria Ocasio-Cortez, D-N.Y.

Republicans are staunchly opposed to including illegal immigrant felons in the proposed cap. The list would also include those charged with a felony or other serious crime, including crimes against a person, drug crimes, gang activity, and violent crimes.

Democrats, the GOP aides said, agreed to exclude those charged as terrorists from the cap, but Democrats insist all other felons should count against it.

Overall, there are currently court-adjudicated removal orders for 180,000 illegal immigrants, including those who have committed felonies.

The spending talks stalled as the two parties were moving closer to funding new border barriers. There is still no final agreement, however, on exactly how much funding to provide and numbers range from $1.3 million to more than $2 billion, the senior Democratic aide said.

Negotiators have not yet agreed to what kind of barriers or where on the border they should be installed.

Republican aides described the negotiators as “still trying to move toward each other” on the barriers.

[Related: Democrats pitch 'cutting edge technology,' but no border wall money]