MOSCOW, Aug. 6 (Xinhua) -- Russian President Vladimir Putin and U.S. President Donald Trump's special envoy Steve Witkoff on Wednesday held talks on Ukraine and the prospects for bilateral ties, said Russian presidential aide Yury Ushakov.

"As for the topics covered, then, first of all, of course, it is the Ukrainian crisis. And the second topic is the prospects for the possible development of strategic cooperation between the United States and Russia," Ushakov said, adding that the talk was "very useful and constructive."

Ushakov said that further details will follow after Trump is briefed on the outcome.

Witkoff previously visited Moscow on April 25 and St. Petersburg on April 11, holding talks with Putin both times.