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An aide to a top Russian official has denied leaking a bugged phone call where a U.S. diplomat could be heard using salty language to describe the European Union, amid suspicions that Moscow was behind the embarrassing episode.

An aide to Russian deputy prime minister, Dmitry Rogozin, was among the first to tweet about the YouTube video. But the aide told The Associated Press that he was surfing a social networking website when he came across the video. He said his decision to repost the video had no connection to his work for the Russian government.

U.S. State Department officials, though, were suspect. The tape itself depicted an apparent conversation between the top U.S. diplomat for Europe, Victoria Nuland, and the U.S. ambassador to Ukraine, Geoffrey Pyatt.

In the audio, voices resembling those of Nuland and Pyatt discussed international efforts to resolve Ukraine's ongoing political crisis. At one point, the Nuland voice colorfully suggested that the E.U.'s position should be ignored. "F--- the E.U.," the voice said.

Nuland has apologized to E.U. officials, but also reacted to the leaked conversation on Friday.

"It was pretty impressive tradecraft," Nuland said. "The audio was extremely clear."

State Department spokeswoman Jen Psaki was less reserved, saying Thursday that Moscow's apparent role in publicizing the video was "a new low in Russian tradecraft."

White House spokesman Jay Carney pointed to the Russian official's tweet and Russia's clear interest in what has become a struggle between pro-Moscow and pro-Western camps in the former Soviet Republic of Ukraine.

"I would say that since the video was first noted and tweeted out by the Russian government, I think it says something about Russia's role," Carney told reporters.

The U.S. has repeatedly denied allegations, many of them from Russian officials, that it is taking sides in the Ukraine crisis and Psaki repeated that stance on Thursday.

"It is no secret that Ambassador Pyatt and Assistant Secretary Nuland have been working with the government of Ukraine, with the opposition, with business and civil society leaders to support their efforts," Psaki said. "It shouldn't be a surprise that at any points there have been discussions about recent events and offers and what is happening on the ground."

The YouTube video was posted on Feb. 4 and is titled the "Marionettes of Maidan" in Russian. Maidan is the name of the main square in the Ukrainian capital of Kiev, which has become the center of opposition protests.

The Associated Press contributed to this report.