U.S. European Command has raised its threat level over worries that Russia is massing forces around eastern Ukraine, where the Pentagon says tensions have escalated in recent weeks.

“We’re discussing our concerns about this increase in tensions and cease-fire violations and regional tensions with NATO allies,” Pentagon spokesman John Kirby told reporters Wednesday.

The situation in Ukraine prompted Joint Chiefs of Staff Chairman Gen. Mark Milley on the same day to connect with his counterparts in both Russia and Ukraine, in an attempt to de-escalate a situation that has prompted fears within Ukraine of a looming Russian offensive.

Gen. Tod Wolters in the past week raised EUCOM’s watch level for Ukraine from possible crisis to potential imminent crisis — the highest level, The New York Times reported Wednesday. EUCOM declined to comment on the threat level change, but said it is monitoring events in Ukraine carefully.