MOSCOW, March 27 (Reuters) - An ally of President Vladimir Putin has warned that Russia has the weapons to destroy any enemy, including the United States, if its own existence is threatened, accusing Washington of underestimating Moscow's nuclear might.

The comments from Nikolai Patrushev, the influential secretary of Russia's Security Council, are the latest from a senior Russian official to raise the spectre of a nuclear showdown between the world's two largest nuclear powers, something Moscow says it wants to avoid.

"American politicians trapped by their own propaganda remain confident that, in the event of a direct conflict with Russia, the United States is capable of launching a preventive missile strike, after which Russia will no longer be able to respond. This is short-sighted stupidity, and very dangerous," Patrushev told the state Rossiiskaya Gazeta newspaper on Monday.

"Russia is patient and does not intimidate anyone with its military advantage. But it has modern unique weapons capable of destroying any adversary, including the United States, in the event of a threat to its existence", he said.

Russia has said that one of the reasons why it sent tens of thousands of troops into Ukraine in February last year in what it calls its "special military operation" was to counter a perceived security threat stemming from Kyiv's rapprochement with the U.S.-led NATO defence alliance.

Since then, Moscow has accused the West, without presenting public evidence, of making nuclear threats against it, and has spoken of its readiness to use nuclear weapons in extreme circumstances if the very existence of the Russian state is imperilled.

On Saturday, President Vladimir Putin announced that Russia would station tactical nuclear missiles in its close ally Belarus, which borders both Ukraine and Russia, sending a warning to NATO over its military support for Kyiv and escalating a standoff with the West.