Leaders say the allies are ‘fully demonstrating their invincibility’ and pledge to bolster security ties as US accuses Pyongyang of supplying weapons to Moscow.

The letters mark the 78th anniversary of Korea’s liberation from Japan’s 1910-45 colonial rule, which is also celebrated as a national holiday in South Korea.

In his letter to Putin on Tuesday, Kim said the two countries’ friendship was forged in World War II with victory over Japan and is now “fully demonstrating their invincibility and might in the struggle to smash the imperialists’ arbitrary practices and hegemony”, state news agency KCNA said.

“I am firmly convinced that the friendship and solidarity … will be further developed into a long-standing strategic relationship in conformity with the demand of the new era,” Kim was quoted as saying in the letter.

“The two countries will always emerge victorious, strongly supporting and cooperating with each other in the course of achieving their common goal and cause.”

The United States has accused North Korea of providing weapons to Russia for its war in Ukraine, including artillery shells, shoulder-fired rockets and missiles. Pyongyang and Moscow have denied any arms transactions.

‘Deeply concerned’

Moscow and Pyongyang – both increasingly isolated from the West and weighted with sanctions – have drawn closer since the Kremlin deployed troops to Ukraine and commenced large-scale hostilities last year.

Last month, Russia’s defence minister stood shoulder to shoulder with Kim as they reviewed North Korea’s newest nuclear-capable missiles and attack drones at a military parade in the capital Pyongyang.

Washington remains “deeply concerned” about North Korea aiding Russia’s war effort in Ukraine and believes Moscow is seeking to increase its cooperation with Pyongyang, US Department of State Deputy Spokesperson Vedant Patel said.

“Any kind of security cooperation or arms deal between North Korea and Russia would certainly violate a series of UN Security Council resolutions,” Patel said at a regular news briefing.

Putin, in his message to Kim, also pledged to bolster bilateral ties.

“I am sure that we will strengthen the bilateral cooperation in all fields for the two peoples’ well-being and the firm stability and security of the Korean peninsula and the whole of Northeast Asia,”  Putin said in a statement distributed by the Kremlin.

The leaders of South Korea, the US and Japan are set to discuss security cooperation over North Korea, Ukraine, and other issues at a trilateral summit on Friday at Camp David.

‘Ugly hostile face of the US’

In a separate KCNA dispatch, Pyongyang’s vice foreign minister, Kim Son Gyong, criticised the US for calling a UN Security Council meeting on North Korea’s human rights situation.

The meeting, set for Thursday and requested by the US, Albania and Japan, would be the first formal public gathering of the 15-member council on the issue since 2017. But China opposed it saying it would only “intensify confrontation and antagonism”.

Kim, the vice minister, said the planned meeting “openly exposed the ugly hostile face of the US filled with a sense of confrontation”, while highlighting the reality of the council that has “fallen into dysfunction under the US’s forced authority and abuse of power”.