US President Donald Trump’s administration considers the sanctions on Russia insufficient and rates them as C on a scale of 1 to 10.

The US Special Presidential Envoy for Russia and Ukraine, Keith Kellogg, said that Washington is considering the possibility of tightening the restrictions on Russia's energy sector.

One can indeed tighten sanctions, especially the latest restrictions on oil production and exports; this has opened up a lot of opportunities to do something, Kellogg told the New York Post.

According to him, the US economic pressure on Russia has not been painful enough.

Washington still has the means to tighten sanctions on Russia's energy sector, but for now their strength is rated as C on a scale of 1 to 10, Kellogg added.