Kim Jong-un, the leader of North Korea, plans to travel to Russia this month to meet with President Vladimir V. Putin to discuss the possibility of supplying Russia with more weaponry for its war in Ukraine and other military cooperation, according to American and allied officials.

In a rare foray from his country, Mr. Kim would travel from Pyongyang, North Korea’s capital, probably by armored train, to Vladivostok, on the Pacific Coast of Russia, where he would meet with Mr. Putin, the officials said. Mr. Kim could possibly go to Moscow, though that is not certain.

Mr. Putin wants Mr. Kim to agree to send Russia artillery shells and antitank missiles, and Mr. Kim would like Russia to provide North Korea with advanced technology for satellites and nuclear-powered submarines, the officials said. Mr. Kim is also seeking food aid for his impoverished nation.

Both leaders would be on the campus of Far Eastern Federal University in Vladivostok to attend the Eastern Economic Forum, which is scheduled to run Sept. 10 to 13, according to the officials. Mr. Kim also plans to visit Pier 33, where naval ships from Russia’s Pacific fleet dock, they said. North Korea celebrates the anniversary of its founding on Sept. 9.

On Wednesday, the White House warned that Mr. Putin and Mr. Kim had exchanged letters discussing a possible arms deal, citing declassified intelligence. A White House spokesman, John F. Kirby, said high-level talks on military cooperation between the two nations were “actively advancing.” U.S. officials declined to give more details on the state of personal ties between the leaders, who are considered adversaries of the United States.