With no deal to fund the government on the horizon, an estimated 800,000 federal employees likely won't get paid until late January.

"If we don't have an agreement I think by midnight on the 8th, which is Tuesday, then payroll will not go out as originally planned on Friday night," White House Acting Chief of Staff Mick Mulvaney said on NBC's "Meet the Press" on Sunday.

Democrats have said they will not give President Donald Trump the $5 billion he has demanded for his promised border wall, while Senate Republican leadership has said the chamber won't vote on anything the president won't sign. Despite working groups convening over the weekend, little progress appears to have been made. The Senate, which convenes at 3 p.m. ET on Monday, isn't scheduled to vote on anything related to government funding, and House lawmakers don't return to Washington until Tuesday evening.

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Approximately 800,000 federal employees are affected by the partial government shutdown; half have been furloughed — forbidden from working during the shutdown — while half are still working with no guarantee of pay. In past shutdowns, furloughed employees have received back pay.

Workers' last paychecks were issued in late December, Mulvaney said.

Depending on their department, government workers are due to receive their paychecks between January 11 and January 17 for the pay period that ran from December 22 to January 5, according to an official at the largest government worker union, American Federation of Government Employees (AFGE), who asked not to be identified because he was not authorized to be quoted by name.

The official also said payroll takes several days to process by departments and then again in the Treasury. If payroll is missed this Friday, the next scheduled pay days are between between January 25 and January 31.

Mulvaney on Sunday said “there might be some who do get paid before the 25th,” but offered no specifics. The AFGE official said off-cycle paychecks are possible, but typically there are only a few thousand per pay cycle.

The president, who has threatened to declare a national emergency and build his wall without funding approval from Congress, encouraged people to plead with their landlords if they struggle to pay bills during the partial shutdown. Landlords in turn should be understanding, he said.

“I would encourage them to be nice and easy. We have a bigger subject that we're doing. It's called "the security of our nation," including terrorism, please. Okay,” Trump said on Friday.