Russia's sovereign wealth fund on Friday said the country was enjoying its best-ever relationship with China.

While Moscow's ties with Bejing have historically been benign, those comments constitute a reiteration of the two countries' strong alliance — at a time of heightened uncertainty and simmering tensions between them and the United States.

"China is definitely a very strategic partner for Russia and we have the best relationship in the history of Russia (and) China right now," said Kirill Dmitriev, CEO of the Russian Direct Investment Fund.

"We have a Russia-China investment fund, which is a partnership between us and (sovereign wealth fund) China Investment Corporation. And today ... we are announcing our participation in NIO," a China-based electric vehicle joint venture, Dmitriev added.

In April, the Kremlin said relations between Moscow and Washington were "in their worst period since the end of the Cold War," and Russian President Vladimir Putin compared U.S. accusations of a Kremlin-led chemical attack in Syria to its justification of the 2003 Iraq invasion.