Russian President Vladimir Putin will visit North Korea for a two-day visit starting Tuesday, both countries announced, amid international concerns about their military cooperation.

Putin is expected to meet North Korean leader Kim Jong Un for talks as they deepen their alignment in the face of separate, intensifying confrontations with Washington. It will be Putin’s first trip to North Korea in 24 years.

North Korea’s official Korean Central News Agency said Putin will pay a state visit on Tuesday and Wednesday at Kim’s invitation. North Korean state media didn’t immediately provide details. Russia confirmed the visit in a simultaneous announcement.

There are growing concerns about an arms arrangement in which Pyongyang provides Moscow with badly needed munitions to fuel Putin’s war in Ukraine in exchange for economic assistance and technology transfers that would enhance the threat posed by Kim’s nuclear weapons and missile program.

Military, economic and other cooperation between North Korea and Russia have sharply increased since Kim visited the Russian Far East in September for a meeting with Putin, their first since 2019.

U.S. and South Korean officials have accused the North of providing Russia with artillery, missiles and other military equipment to help prolong its fighting in Ukraine, possibly in return for key military technologies and aid. Both Pyongyang and Moscow have denied accusations about North Korean weapons transfers.

Any weapons trade with North Korea would be a violation of multiple U.N. Security Council resolutions that Russia, a permanent U.N. Security Council member, previously endorsed.

Andrei Lankov, an expert on North Korea at Kookmin University in Seoul, noted that in exchange for providing artillery munitions and short-range ballistic missiles, Pyongyang hopes to get higher-end weapons from Moscow.

Lankov noted that while Russia could be reluctant to share its state-of-the-art military technologies with North Korea, it’s eager to receive munitions from Pyongyang. “There is never enough ammunition in a war, there is a great demand for them,” Lankov told The Associated Press.

There were signs that Kim was preparing to throw a lavish celebration for Putin as he tries to boost the visibility of their relationship to his domestic audience. The North Korea-focused NK News website said Monday that its analysis of commercial satellite images suggest that the North is possibly preparing a huge parade at a square in the country’s capital, Pyongyang.

Kim in recent months has made Russia his primary focus as he tries to strengthen his regional footing and expand cooperation with nations confronting the United States, embracing the idea of what he portrays as a “new Cold War. ”

During telephone talks with South Korea’s vice foreign minister on Friday, U.S. Deputy Secretary of State Kurt Campbell raised concern that Putin’s visit to the North would result in further military cooperation between the countries that potentially undermines stability in the region, Seoul’s Foreign Ministry said in a statement.

“The list of countries willing to welcome Putin is shorter than ever, but for Kim Jong Un, this visit is a victory,” said Leif-Eric Easley, a professor at Ewha University in Seoul.

“Not only does the summit upgrade North Korea’s status among countries standing against the U.S.-led international order, it also helps bolster Kim’s domestic legitimacy. Russia cannot replace China economically, but increasing cooperation with Moscow shows that Pyongyang has options.”

Putin first visited Pyongyang in July 2000, months after his first election when he met with Kim’s father, Kim Jong Il, who ruled the country then.

Moscow has said it “highly appreciates” Pyongyang’s support for Russia’s military action in Ukraine and mentioned its “close and fruitful cooperation” at the United Nations and other international organizations.

Russia and China have repeatedly blocked the U.S. and its partners’ attempts to impose fresh U.N. sanctions on North Korea over its barrage of banned ballistic missile tests.

In March, a Russian veto at the United Nations ended monitoring of U.N. sanctions against North Korea over its nuclear program, prompting Western accusations that Moscow is seeking to avoid scrutiny as it allegedly violates the sanctions to buy weapons from Pyongyang for use in Ukraine.

During a news conference in March, South Korean Defense Minister Shin Wonsik said North Korea had already shipped about 7,000 containers filled with munitions and other military equipment to Russia. In return, Shin said that North Korea had received more than 9,000 Russian containers likely filled with aid.

Kim has also used Russia’s war in Ukraine as a distraction to dial up his weapons development as he pursues a nuclear arsenal that could viably threaten the United States and its Asian allies. This prompted the U.S. and South Korea to expand their combined military exercises and sharpen their nuclear deterrence strategies built around strategic U.S. assets.

Earlier this year, Putin sent Kim a high-end Aurus Senat limousine, which he had shown to the North Korean leader when they met for a summit in September. Observers said the shipment violated a U.N. resolution aimed at pressuring the North to give up its nuclear weapons program by banning the supply of luxury items to North Korea.

Putin has continuously sought to rebuild ties with Pyongyang as part of efforts to restore his country’s global clout and its Soviet-era alliances. Moscow’s ties with North Korea weakened after the 1991 Soviet collapse. Kim Jong Un first met with Putin in 2019 in Russia’s eastern port of Vladivostok.

After North Korea, the Kremlin said Putin will also visit Vietnam on Wednesday and Thursday. He is set to meet in Hanoi with Gen. Nguyen Phu Trong, the secretary general of the Vietnamese Communist Party, President To Lam, Prime Minister Pham Minh Chinh and National Assembly Chairman Tran Thanh Man.

They plan to discuss “prospects for the continued development of a comprehensive strategic partnership between Russia and Vietnam in the trade and economy, scientific and technology, and humanitarian fields,” the Kremlin said in a statement.

The United States, which has spent years strengthening ties and accelerating trade with Vietnam, criticized Putin’s planned visit.

“As Russia continues to seek international support to sustain its illegal and brutal war against Ukraine, we reiterate that no country should give Putin a platform to promote his war of aggression and otherwise allow him to normalize his atrocities,” a U.S. Embassy spokesperson in Vietnam said in a statement.

“If he is able to travel freely, it could normalize Russia’s blatant violations of international law and inadvertently send the message that atrocities can be committed in Ukraine and elsewhere with impunity, worsening human suffering, and prolonging the path to sustainable peace and justice,” the statement said.