Vladimir Putin promised to build trade and security systems with North Korea that are not controlled by the West as he heads to Pyongyang for the first time in 24 years.
Putin pledged his unwavering support in a letter published by North Korean state media on Tuesday ahead of his planned visit to the country.
In the letter, printed in North Korea's Rodong Sinmun, the ruling Workers' Party mouthpiece, the Russian president said the two countries have developed good relations and partnerships over the past 70 years based on equality, mutual respect and trust.
"We will develop alternative mechanisms of trade and mutual settlements that are not controlled by the West, and jointly resist illegitimate unilateral restrictions," Putin wrote. "And at the same time – we will build an architecture of equal and indivisible security in Eurasia."
He thanked North Korea for supporting what Russia calls its special military operation in Ukraine, and vowed support for Pyongyang's efforts to defend its interests despite what he called "US pressure, blackmail and military threats".
North Korean state media also published articles praising Russia and supporting its operations in Ukraine, calling them a "sacred war of all Russian citizens".
"The Korean people will always be on the side of the Russian government and people, extending full support and solidarity to their struggle to defend the national sovereignty and security interests," KCNA said in a commentary.
US State Department spokesperson Matthew Miller repeated charges on Monday that North Korea had supplied "dozens of ballistic missiles and over 11,000 containers of munitions to Russia" for use in Ukraine.
He said the United States had seen Putin "get incredibly desperate over the past few months" and look to Iran and North Korea to make up for equipment lost on the battlefield.
Moscow and Pyongyang have denied arms transfers.
Russia has promised cooperation with North Korea on a range of humanitarian, economic, trade, and military areas and has blocked efforts at the United Nations Security Council to monitor and impose new sanctions on Pyongyang.
After North Korea, Putin will visit Vietnam on June 19-20.

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