Russian foreign minister Sergei Lavrov has said that Russia would respect the will of Crimeans ahead of a contentious referendum but admitted Moscow had no "common vision" with the US, despite "useful" talks with John Kerry in London.

He added that the Crimean example "cannot be examined without historical contexts".

"Crimea means more to Russia than the Falklands mean to Britain," Lavrov said.

He reassured the West that Russia had no plans to intervene in southeastern Ukraine but warned that the rights of Russians in Crimea "should be protected and secured".

Sunday's referendum to decide whether Crimea wanted to stay within Kiev's orbit or cede to Moscow was an example of the UN principle of self-determination, he claimed.

"Kerry made no threats regarding Russia. Our partners know that [economic and diplomatic] sanctions are counter-productive," he told a press conference.