Russian President Vladimir Putin is to visit North Korea for the first time in 24 years on Tuesday.
Mr Putin will meet North Korean leader Kim Jong Un for talks in the capital, Pyongyang.
The two leaders last met in September at the Vostochny cosmodrome in Russia’s far east, but this is Mr Putin’s first visit to Pyongyang since 2000.
The United States said it was concerned about the “deepening relationship between these two countries”.
The Kremlin has described the event as a “friendly state visit” with Russian media reporting Mr Putin and Mr Kim may sign a partnership agreement, including on security issues, and will give joint statements to the media.
A parade in Kim Il Sung square is anticipated. Mr Putin is also expected to watch a concert and visit the Orthodox Church of the Life-Giving Trinity in Pyongyang, the only orthodox church in North Korea.
There are reports Mr Putin will stay at the Kumsusan guesthouse in Pyongyang, where Chinese leader Xi Jinping last stayed during his state visit to North Korea in 2019.
Mr Putin is expected to arrive with his new defence minister, Andrei Belousov, while Foreign Minister Sergei Lavrov and Deputy Prime Minister Alexander Novak will also be part of the delegation.
The Russian president praised North Korea for “firmly supporting” Moscow’s war in Ukraine ahead of his visit, in a letter published in North Korean state media.
He promised to build trade and security systems with Pyongyang “that are not controlled by the West”, in the article printed in Rodong Sinmun, North Korea’s ruling party mouthpiece.
President Putin also vowed support for Pyongyang’s efforts to defend its interests despite what he called “US pressure, blackmail and military threats”.
Mr Kim said last week that ties with Russia had “developed into an unbreakable relationship of comrades-in-arms”.
During their meeting last year, Mr Putin said he saw “possibilities” for military cooperation with North Korea, while Mr Kim wished Russia’s president “victory” in Ukraine.
The White House said the US is concerned about closer ties between Russia and North Korea.
“We’re not concerned about the trip” by Mr Putin, National Security Council spokesman John Kirby told reporters on Monday. “What we are concerned about is the deepening relationship between these two countries.”
John Nilsson-Wright, head of the Japan and Koreas programme at Cambridge University’s Centre for Geopolitics, said Mr Putin is “strengthening ties with its old Cold War partner” in an effort to “counter any suggestion that the US and its allies have been able to isolate Moscow”.
“He is bolstering relations between authoritarian regimes at a time when democratic governments are in a defensive position, confronting global security challenges” in the Middle East, East Asia and Ukraine, he added.
