A conflict on the Korean peninsula would have "catastrophic consequences", and Russia's foreign ministry is working "behind the scenes" on finding a political solution to the North Korea crisis, the RIA news agency cited a senior Russian diplomat as saying on Tuesday.

Cited by RIA, Mikhail Ulyanov, the head of the non-proliferation and arms controls department at Russia's foreign ministry, also said the U.S. approach to North Korea was a dead end and the tool of sanctions against the North had almost been exhausted.

North Korean Foreign Minister Ri Yong Ho said on Monday that U.S. President Donald Trump had declared war on North Korea and that Pyongyang reserves the right to take countermeasures, including shooting down U.S. strategic bombers even if they are not in the country's air space.