SEOUL, South Korea (AP) — Joined by his top military officials handling his nuclear-capable weapons and munitions factories, North Korean leader Kim Jong Un arrived in Russia on Tuesday, where he is expected to hold a rare meeting with President Vladimir Putin that has sparked Western concerns about a potential arms deal for Moscow’s war in Ukraine.

North Korea’s official news agency said Kim boarded from the capital, Pyongyang, on Sunday afternoon, and that he was accompanied by unspecified members of the country’s ruling party, government and military.

Jeon Ha Gyu, spokesperson of South Korea’s Defense Ministry, said in a briefing that the South’s military assesses that Kim’s train crossed into Russia sometime early Tuesday. He didn’t elaborate how the military obtained the information.

North Korean state media showed photographs of Kim walking past honor guards and crowds of civilians holding the national flag and flowers, and also of him waving from his green-and-yellow armored train before it left the station. Kim’s delegation likely includes his foreign minister, Choe Sun Hui, and his top military officials, including Korean People’s Army Marshals Ri Pyong Chol and Pak Jong Chon.

A group of senior officials were at the station to give the leader a “hearty send-off,†according to the Korean Central News Agency, which did not specify whether the train had crossed the border. Citing unidentified Russian regional officials, Japanese broadcaster TBS reported that Kim’s train crossed the border and arrived in the border town of Khasan.

A brief statement on the Kremlin’s website on Monday said the visit is at Putin’s invitation and would take place “in the coming days.†KCNA said the leaders would meet — without specifying when and where.

Kremlin spokesperson Dmitry Peskov said that Putin and Kim will lead their delegations in talks and could also meet “one-on-one if necessary.†He added that Putin will host an official dinner for Kim.

The talks will focus on bilateral ties, Peskov said. “As with any of our neighbors, we feel obliged to develop good, mutually beneficial relations,†he added.

A possible venue is the eastern Russian city of Vladivostok, where Putin arrived Monday to attend an international forum that runs through Wednesday, according to Russia’s TASS news agency. The city, located about 425 miles (680 kilometers) north of Pyongyang, was also the site of Putin’s first meeting with Kim in 2019.

The visit would be Kim’s first foreign trip since the COVID-19 pandemic, which had forced North Korea to enforce tight border controls for more than three years to shield its poor health care system. While Kim has shown to be more comfortable using planes than his famously flight-adverse father, he has also used his personal train for previous meetings with Putin, Chinese President Xi Jinping and former U.S. President Donald Trump, reviving a symbol of his family’s dynastic rule.

Associated Press journalists near the North Korea-Russia frontier saw a green train with yellow trim — similar to one used by the reclusive Kim during previous foreign trips — at a station on the North Korean side of a border river.

The train was seen moving back and forth between the station and the approach to the bridge that connects the countries, but ithad not crossed the bridge as of 7 p.m. local time (1000 GMT).

Citing unidentified South Korean government sources, the Chosun Ilbo newspaper reported 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 Presidential Office, Defense Ministry and ´ºÉ«Ö±²¥ 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 as they expand their cooperation in the face of deepening confrontations with the United States.

According to U.S. officials, Putin could focus on and other ammunition to refill declining reserves as he seeks to defuse a Ukrainian counteroffensive and show that he’s capable of grinding out a long war of attrition. That could potentially put more pressure on the U.S. and its partners to pursue negotiations as concerns over a protracted conflict grow despite their huge shipments of advanced weaponry to Ukraine in the past 17 months.

“Arms discussions between Russia and the DPRK are expected to continue during Kim Jong Un’s trip to Russia,†said White House ´ºÉ«Ö±²¥ Security Council spokesperson Adrienne Watson, using the abbreviation for North Korea’s official name of the Democratic People’s Republic of Korea. “We urge the DPRK to abide by the public commitments that Pyongyang has made to not provide or sell arms to Russia.â€

State Department spokesman Matthew Miller said Washington will monitor the meeting closely, reminding both countries that “any transfer of arms from North Korea to Russia would be a violation of multiple U.N. Security Council resolutions,†and that the U.S. “will not hesitate to impose new sanctions.â€

North Korea has possibly tens of millions of artillery shells and rockets based on Soviet designs that could potentially give a huge boost to the Russian army, analysts say.

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 U.S., South Korea, and Japan. Based on North Korean state media photos, Kim’s delegation possibly includes Pak Thae Song, chairman of North Korea’s space science and technology committee, and Navy Admiral Kim Myong Sik, who are linked with North Korean efforts to acquire spy satellites and nuclear-capable submarines.

Kim Jong Un also seems to be bringing Jo Chun Ryong, a ruling party official in charge of munitions policies who had accompanied the leader on his recent tours to factories producing artilleries and missiles.

After decades of a complicated, hot-and-cold relationship, Russia and North Korea have been drawing closer since Moscow’s invasion of Ukraine in 2022. The bond has been driven by Putin’s need for war help and Kim’s efforts to boost the visibility of his partnerships with traditional allies Moscow and Beijing as he tries to break out of diplomatic isolation and have North Korea be part of a united front against Washington.

While using the distraction caused by the Ukraine conflict to ramp up its weapons development, North Korea has repeatedly blamed Washington for the crisis in Ukraine, claiming the West’s “hegemonic policy†justified a Russian offensive in Ukraine to protect itself.

North Korea is the only nation besides Russia and Syria to recognize the independence of two Russian-backed separatist regions in eastern Ukraine — Donetsk and Luhansk -– and it has also hinted at an interest in sending construction workers to those areas to help with rebuilding efforts.

Russia -– along with China -– have blocked U.S.-led efforts at the U.N. Security Council to strengthen sanctions on North Korea over its intensifying missile tests while accusing Washington of worsening tensions with Pyongyang by expanding military exercises with South Korea and Japan.

The United States has been accusing North Korea since last year of providing Russia with arms, including artillery shells sold to the Russian mercenary group Wagner. Both Russian and North Korean officials denied such claims. But speculation about the countries’ military cooperation grew after Russian Defense Minister Sergei Shoigu made a rare visit to North Korea in July, when Kim invited him to an arms exhibition and a massive military parade in the capital where he showcased ICBMs designed to target the U.S. mainland.

Following that visit, Kim toured North Korea’s weapons factories, including a facility producing artillery systems where he urged workers to speed up the development and large-scale production of new kinds of ammunition. Experts say Kim’s visits to the factories likely had a dual goal of encouraging the modernization of North Korean weaponry and examining artillery and other supplies that could possibly be exported to Russia.

Some analysts say a potential meeting between Kim and Putin would be more about symbolic gains than substantial military cooperation.

Russia, which has always closely guarded its most important weapons technologies, even from key allies such as China, could be unwilling to make major technology transfers with North Korea for what is likely to be limited war supplies transported over a small rail link between the countries, they say. ___

Associated Press journalists Jim Heintz in Tallinn, Estonia, Aamer Madhani and Matthew Lee in Washington and Dake Kang and Ng Han Guan in Fangchuan, China, contributed.

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