Russia and North Korea confirmed on Monday that North Korean leader Kim Jong-un will visit Russia in a highly anticipated meeting with President Vladimir Putin that has sparked western concerns about a potential arms deal that could fuel Moscow’s war in Ukraine.

A statement on the Kremlin’s website said Kim’s visit is at Putin’s invitation and would take place “in the coming days.” The visit also was reported by North Korea’s official KCNA news agency, saying he would meet with Putin.

Associated Press journalists near the North Korean-Russia border spotted a green train with yellow trim — similar to the train used by Kim Jong-un during his previous foreign trips — on a station at the North Korean side of a border river.

It was unclear whether Kim was on the train, which was seen moving back and forth between the station and the approach towards the bridge that connects the countries but had not crossed the bridge as of 7pm (1000 GMT).

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. Japan’s Kyodo news agency cited Russian officials as saying that Kim was possibly heading for Russia on his personal train.

South Korea’s Presidential Office didn’t immediately confirm those details.

US 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 US.

A possible venue for the meeting is Vladivostok, where Putin arrived on Monday to attend an international forum that runs till Wednesday, according to Russia’s TASS news agency.

The city was also the site of Putin’s first meeting with Kim in 2019. According to US officials, Putin could focus on securing more supplies of North Korean artillery to refill declining reserves as he seeks to defuse a Ukrainian counteroffensive.