The U.S. military is set to put almost half of its 8,500 South Korean civilian workers on furlough, as the two sides bicker over the Trump administration’s demands for a massive increase in troop funding.

About 4,000 workers have been told not to report to American military bases in South Korea as of Wednesday, if the two countries can’t find some way to extend a cost-sharing deal that expired Dec. 31. A breakthrough seems unlikely with President Donald Trump asking for as much as a five-fold increase and South Korea showing no signs of paying anywhere near that much.

The furloughs, which the Hankyoreh newspaper said would be the first of their kind, will put new pressure on an alliance that Trump has repeatedly criticized since taking office three years ago. The move comes as the U.S. military struggles to keep coronavirus outbreaks from disrupting operations in South Korea and elsewhere and the allies watch for fresh provocations from North Korean leader Kim Jong Un.