The U.S. company overseeing operations and maintenance services at Turkey’s southern İncirlik air base has laid off almost half of its staff, Turkish news site Dokuz8 Haber reported on Tuesday.

The report arrives as questions loom over the future of the base, which hosts U.S. nuclear warheads about 100 miles from Turkey’s border with Syria, amid tensions between Washington and Ankara.

The contracts of a total of 424 of 890 staff working with Vectrus System Corporation will be terminated by Feb. 20 at the latest, it said citing a notice sent by the company to the Union of Defence Industry and Allied Workers (Türk Harb-Is).

The union responded to the decision by Vectrus calling on the company, which provides global government services in 22 countries with approximately 6,700 employees, to reconsider the move.

Main opposition Republican People’s Party (CHP) Adana Deputy Orhan Sümer reacted the call by the U.S. company, saying Vectrus should know that Turkish workers “are not people that can be hired and fired as the United States pleases’’.

Turkish President Recep Tayyip Erdoğan in December said Turkey could shut down its Incirlik air base, in response to threats of U.S. sanctions and a separate U.S. Senate resolution that recognising the mass killings of Armenians a century ago as genocide.