North Korean leader Kim Jong Un vowed his country will “invariably support” Russia’s war in Ukraine as he met Russia's defense chief, the North’s state media reported Saturday.

A Russia military delegation led by Defense Minister Andrei Belousov arrived in North Korea on Friday, amid growing international concern about the two countries’ expanding cooperation after North Korea sent thousands of troops to Russia last month.

The official Korean Central News Agency said that Kim and Belousov reached “a satisfactory consensus” on boosting strategic partnership and defending each country’s sovereignty, security interests and international justice in the face of the rapidly-changing international security environments in a Friday meeting.

Kim said that North Korea “will invariably support the policy of the Russian Federation to defend its sovereignty and territorial integrity from the imperialists’ moves for hegemony,” KCNA said.

North Korea has supported Russia’s invasion of Ukraine, calling it a defensive response to what both Moscow and Pyongyang call NATO’s “reckless” eastward advance and U.S.-led moves to stamp out Russia’s position as a powerful state.

Kim slammed a U.S. decision earlier in November to let Ukraine strike targets inside Russia with U.S.-supplied longer-range missiles as a direct intervention in the conflict. He called recent Russian strikes on Ukraine “a timely and effective measure" demonstrate Russia's resolve, KCNA said.

According to U.S., Ukrainian and South Korean assessments, North Korea has sent more than 10,000 troops to Russia and some of them have already begun engaging in combat on the frontlines. U.S., South Korean and others say North Korea has also shipped artillery systems, missiles and other conventional weapons to replenish Russia’s exhausted weapons inventory.

Both North Korea and Russia haven’t formally confirmed the North Korean troops’ movements, and have steadfastly denied reports of weapons shipments.

South Korea, the U.S. and their partners are concerned that Russia could give North Korea advanced weapons technology in return, including help to build more powerful nuclear missiles.

Last week, South Korean national security adviser Shin Wonsik told a local SBS TV program that that Seoul assessed that Russia has provided air defense missile systems to North Korea. He said Russia also appeared to have given economic assistance to North Korea and various military technologies, including those needed for the North’s efforts to build a reliable space-based surveillance system.

North Korean leader calls for expanding his nuclear forces in the face of alleged US threats

Belousov also met North Korean Defense Minister No Kwang Chol on Friday. During a dinner banquet later the same day, Belousov said the the two countries' strategic partnership was crucial to defend their sovereignty from aggression and the arbitrary actions of imperialists, KCNA said.

In June, Kim and Putin signed a treaty requiring both countries to provide immediate military assistance if either is attacked. It's considered the two countries’ biggest defense deal since the end of the Cold War.