(AP) — President Donald Trump says he and Russian President Vladimir Putin have agreed to begin “negotiations” on ending Ukraine war.

The Republican said in a social media post Wednesday disclosing a call between the two leaders that they would “work together, very closely.”

The call followed a prisoner swap that resulted in Russia releasing American schoolteacher Marc Fogel, of Pennsylvania, after more than three years of detention.

Alexander Vinnik, a convicted Russian criminal, is being freed as part of a swap that saw Moscow’s release of Fogel, two U.S. officials confirmed Wednesday. The officials spoke on the condition of anonymity to discuss the swap.