Putin and Kim Sign Pact Pledging Mutual Support Against ‘Aggression’

President Vladimir V. Putin of Russia and North Korea’s leader, Kim Jong-un, revived a Cold War-era mutual defense pledge between their nations on Wednesday, as the Kremlin deepened its security relationship with North Korea and vowed solidarity in challenging the United States.

Neither Russia nor North Korea immediately released the text of the new treaty. But Mr. Putin, speaking at a joint briefing in Pyongyang after the two leaders signed the document, said the pact called for the nations to aid one another in the event of “aggression” against either country. Mr. Kim claimed the new “treaty” elevated the two countries’ relations to an “alliance.”

Mr. Putin did not say whether the new agreement would require immediate and full-fledged military intervention in the event of an attack, as the now-defunct 1961 treaty between Moscow and Pyongyang specified during the days of the Cold War.

The pledge of mutual assistance is likely to further alarm Washington and its allies. It could presage not only deeper support by North Korea for Russia’s war in Ukraine but also greater support from Moscow in aiding Mr. Kim’s quest for better-functioning nuclear weapons, missiles, submarines and satellites — a development that would increase anxiety among America’s Asian allies, especially South Korea.

Both leaders heralded the agreement as the beginning of a new era in their relations.

Mr. Putin, speaking on his first trip to North Korea in nearly a quarter century, cast possible Russian military support for Pyongyang as a logical response to the West’s supplying weapons to Ukraine, which he claimed violated “various international obligations.”

Russia “does not exclude the development of military-technical cooperation” with North Korea, he said, threatening to support the ambitions of a military that the United Nations — backed by Russia — has been trying to defang for years.