MOSCOW — President Vladimir V. Putin of Russia made a public show of support for North Korea on nuclear disarmament, seeming to undermine President Trump’s approach to nuclear diplomacy, as Mr. Putin and Kim Jong-un on Thursday wrapped up their first summit meeting.

Russian officials have long insisted they wanted to support Mr. Trump’s efforts at one-on-one nuclear negotiations with Mr. Kim, the North Korean leader. But speaking to reporters after the meeting in Vladivostok, on Russia’s Pacific Ocean coast, Mr. Putin said that North Korea needs security guarantees from more nations than just the United States before abandoning its nuclear arsenal.

Mr. Putin also reiterated Russian backing for a gradual process of trading disarmament for sanctions relief. “If we take one step forward and two backward, then we would fail to achieve the desired result,” Mr. Putin said. “But it will eventually be possible to achieve this goal, if we move forward gradually and if we respect each other’s interests.”

At talks in February in the Vietnamese capital, Hanoi, Mr. Trump had proposed a “big deal” to lift punishing economic sanctions in return for a quick and complete elimination of North Korea’s nuclear weapons program. Mr. Kim offered, instead, only a partial dismantling of nuclear facilities — while keeping his arsenal of nuclear warheads and missiles — in exchange for relief from the most harmful sanctions.