However Sergei Lavrov called his London meeting with John Kerry "constructive".
Mr Kerry said the US was "deeply concerned" about Russia sending troops to the Ukraine border and in Crimea.
The two foreign ministers met amid tight security at the US ambassador's residence in London
Mr Lavrov said Moscow would respect the result of Sunday's
referendum in Crimea on whether to join Russia but Mr Kerry said the US
would not recognise it.
Mr Kerry said the US was "deeply concerned" about Russia sending troops to the Ukraine border and in Crimea.
