Putin Threatens to Arm North Korea, Escalating Tension With West Over Ukraine

President Vladimir V. Putin of Russia directly warned the United States and its allies that he is willing to arm North Korea if they continue to supply Kyiv with sophisticated weapons that have struck Russian territory, raising the stakes for the Western powers backing Ukraine.

Mr. Putin made the threat in comments to reporters traveling with him late Thursday in Vietnam before he flew home to Russia after a trip there and to North Korea. He had made a similar, though significantly less overt, threat a day earlier in Pyongyang, where he revived a Cold War-era mutual defense pact with North Korea’s leader, Kim Jong-un. The pact requires each nation to provide military assistance to the other “with all means at its disposal” in the event of an attack.

Mr. Putin cast his threat to arm Pyongyang, in violation of United Nations sanctions, as a response to decisions by the United States and its allies in recent months to allow Ukraine to make certain strikes on Russian territory with their weapons. The White House made that decision last month, but maintained its prohibition on longer-range attacks deeper in the country with U.S. arms.

“Those who supply these weapons believe that they are not at war with us,” Mr. Putin said. “Well, as I said, including in Pyongyang, then we reserve the right to supply weapons to other regions of the world.”

“And where will they go next?” Mr. Putin asked of the weapons, suggesting that North Korea could then sell the Russian arms to other rogue actors hostile to the United States and its allies around the world.

Though Mr. Putin didn’t say what weapons he would give to North Korea, Mr. Kim is seeking to advance his nuclear warheads, missiles, submarines and satellites — all areas where Russia