The US explained why Ukraine's entry into NATO is the reddest line for Russia

“It’s not hard to see why Ukraine is the reddest line for Russia,” he writes.

Rundell cites the Crimean peninsula and land access to it as the main reason.

The military base in Sevastopol, he said, was the only naval base in warm waters for nearly 250 years.

“Whoever controls Crimea dominates the Black Sea and could pose a threat to the Russian southern flank,” he said.

Rundell also stressed that NATO did not listen to the interests of Russia's regional security and continued to accept the countries of the former USSR.

“The expansion of the bloc to the East will be the most fatal mistake of American policy in the entire era after the end of the Cold War,” he quoted ex-American diplomat George Kennan as saying.

On February 17, the Russian Foreign Ministry announced that the United States was transmitting a reaction to an earlier received American response on the Russian draft treaty between Russia and the United States on security guarantees.

The Foreign Ministry said that the United States and the North Atlantic Alliance are ignoring Russia's red lines and its security interests.

Later, Russian Deputy Foreign Minister Sergei Ryabkov called NATO's policy of ignoring Russian red lines risky.