"[The] U.S. government has seen nothing so far that corroborates Russian allegations of a 'Crimea incursion' and Ukraine has strongly refuted them," he tweeted on Thursday.
In his words, Russia has a record of frequently levying false accusations at Ukraine "to deflect attention from its own illegal actions."
The U.S. ambassador reiterated his country's position on Crimea's status.
Read alsoUkraine's Foreign Ministry issues statement condemning Russia's provocations"Our view on Crimea's status is well known. Crimea is, and will always remain, part of Ukraine," he wrote on Twitter.
"We condemn and call for an immediate end to the Russian occupation of Crimea," he added.
According to him, U.S. Crimea-related sanctions will remain in place until Russia returns the peninsula to Ukraine.
