An apparently bugged phone conversation in which a senior American diplomat disparages the European Union over the Ukraine crisis has been posted online.
A voice resembling that of Assistant Secretary of State Victoria Nuland refers to the EU using a four letter word.
The audio also has a frank exchange apparently between Ms Nuland and the US Ambassador to Ukraine, Geoffrey Pyatt, about America's strategy on how to work with Ukraine's main opposition leaders, the BBC reports.
The US said Ms Nuland had apologised for the reported comments.
The alleged conversation appeared on YouTube on Thursday after Russia accused Washington of meddling in Ukraine.
The 4min 10s video was called "Maidan's puppets" in Russian - a reference to the square in the Ukrainian capital, Kiev, where pro-EU protests have been held for months. A transcription of the whole conversation was also posted in Russian.
Russia has itself been widely accused of intervening in Ukraine, using its economic clout to persuade President Victor Yanukovych to abandon closer ties with Brussels in favour of Russia and other former Soviet states.
At one point, the female speaker mentions the UN and its possible role in trying to find a solution to the Ukraine stand-off. She says: "So that would be great, I think, to help glue this thing and have the UN help glue it and you know..." she then uses the graphic swear word about the EU.
The male replies: "We've got to do something to make it stick together, because you can be pretty sure that if it does start to gain altitude the Russians will be working behind the scenes to try to torpedo it."
The officials also discuss frankly the merits of the three main Ukrainian opposition leaders - Vitaly Klitschko, Arseniy Yatseniuk and Oleh Tyahnybok