President Donald Trump speaks to U.S. troops at the Osan Airbase on June 20, 2019 in Pyeongtaek, South Korea. Getty

Seoul, South Korea — The U.S. military force in South Korea has issued a 60-day notice of potential furlough to the 9,000 Korean employees who support the American deployment in the country. The warning of a possible involuntary leave comes amid a standoff between the Trump administration and the key U.S. ally over how much money the South Korean government contributes to maintain the roughly 28,500-strong American troop presence.

"United States Forces Korea (USFK) began providing Korean National employees today with a 60-day notice of a potential administrative furlough that could occur on April 1, 2020," the U.S. military said in a press release.

The current funding agreement between the two governments expired at the end of 2019, but the U.S. military has been using reserve funds to keep paying the Korean employees since then.

Get Breaking News Delivered to Your Inbox

"Without the Republic of Korea's continued commitment to share the cost of employing our Korean National workforce, USFK will soon exhaust programmed funds available to pay their salaries and wages," the U.S. military said in a statement.

South Korea has helped support U.S. troops in the country- who serve as a strong deterrent to neighboring North Korea — under a so-called Special Measures Agreement since 1991. Negotiations over the next iteration of that SMA, laying out terms for the funding of the American military presence for the year ahead, have stalled over the Trump administration's demand that Seoul dramatically increase its contribution.

President Trump has pushed various U.S. allies to cough up more money for shared security burdens in both Europe and Asia. Six rounds of negotiations with Seoul have failed to break the deadlock.

Senior Trump administration officials have repeatedly called South Korea a "wealthy" host nation and suggested it could afford a "substantial increase" in its contribution. The White House has not denied reports that it is seeking about $5 billion per year from Seoul. Under the 2019 SMA, Seoul agreed to pay about $870 million.

"Things are very different this year," Son Gi-O, secretary-general of the USFK Korean Employees Union, told CBS News in a phone interview Wednesday. "We've already volunteered to work without payment but were told that this is not possible. I've heard that some people are looking for part-time jobs during the time while we won't be paid. We have to maintain a living, you know?"

He also voiced concerns that the furlough of the Korean support staff could pose a security threat, as the bases might not function as smoothly.

"All those who live here, from the soldiers to the soldiers' family members, would all have a hard time," Son told CBS News. "This has never happened since the U.S. forces have been in Korea!"

U.S. military newspaper Stars and Stripes reported that a man attending a town hall-style meeting for Korean employees, "drew applause when he asked if Korean National employees would get a fivefold raise if the South Koreans agree to pay four or five times more."

South Korean officials have continued to voice hopes that "a reasonable and equitable agreement should be reached" since the last talks, held in Washington on January 14 and 15, failed to bring any breakthrough.