SEOUL, South Korea (AP) — A North Korean train presumably carrying North Korean leader Kim Jong Un has departed for Russia for a possible meeting with Russian President Vladimir Putin, South Korean media said Monday.

Citing unidentified South Korean government sources, the Chosun Ilbo newspaper reported that the train likely left the North Korean capital of Pyongyang on Sunday evening and that a Kim-Putin meeting is possible as early as Tuesday.

The Yonhap news agency and some other media published similar reports. South Korea’s National Intelligence Service didn’t immediately confirm those details.

U.S. officials released intelligence last week that North Korea and Russia were arranging a meeting between their leaders that would take place within this month as they expand their cooperation in the face of deepening confrontations with the United States.

According to U.S. officials, Putin could focus on securing more supplies of North Korean artillery and other ammunition to refill draining reserves and put further pressure on the West to pursue negotiations amid concerns about a protracted conflict in Ukraine.

In exchange, Kim could seek badly needed energy and food aid and advanced weapons technologies, including those related to intercontinental ballistic missiles, nuclear-capable ballistic missile submarines and military reconnaissance satellites, analysts say.

There are concerns that potential Russian technology transfers would increase the threat posed by Kim’s growing arsenal of nuclear weapons and missiles that are designed to target the United States, South Korea, and Japan.