Ukraine reserves the right to make decisions about North Korean workers entering Russia-controlled areas in its eastern Donbas breakaway region, a U.S. State Department spokesperson said Wednesday.

The comments came after the Russian ambassador to North Korea suggested earlier this week that Pyongyang could send workers to two self-declared republics in Donbas despite U.N. sanctions prohibiting such activity.

“It certainly is an affront to the sovereignty of Ukraine,” State Department spokesperson Ned Price said at a press briefing on Wednesday. “The Donbas, eastern Ukraine, belongs to Ukraine and Ukraine alone.”

However, Ukraine will have to fight to retake Donbas before