MOSCOW: Russia on Friday denied leaking the United States' written response to its security guarantee demands to Spanish newspaper El Pais after US Undersecretary of State Victoria Nuland blamed Moscow for the leak.

Commenting on Nuland's allegations made in an interview with Russia's TASS news agency, Russia's embassy to the United States called them "bewildering" and said that "instead of focusing on the essence of Russian concerns, the American side is engaging in conspiracy theories".

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Moscow has demanded guarantees from Washington and NATO that Ukraine will not be allowed to join the military bloc. Russia has amassed over 100,000 troops close to the Ukrainian borders, but denies planning an invasion.