Kim Jong-un has boarded a train to Vietnam for his second summit with US president Donald Trump, North Korea state media have confirmed.

The North Korean leader was accompanied by Kim Yong-chol, who has been a key negotiator in talks with the US, and by his sister Kim Yo-jong, the North’s official Korean Central News Agency reported.

There was a report of a green and yellow train similar to one used in the past by Kim crossing into the Chinese border city of Dandong via a bridge. Kim’s overseas travel plans are routinely kept secret and it could take more than two days for the train to travel thousands of miles through China to Vietnam.

The Trump-Kim meeting is scheduled for Wednesday and Thursday in Hanoi.

Their first summit last June in Singapore ended without substantive agreements on the North’s nuclear disarmament and triggered a months-long stalemate in negotiations as Washington and Pyongyang struggled with the sequencing of North Korea’s nuclear disarmament and the removal of US-led sanctions against the North.

The North Korean leader is accompanied by his sister, Kim Yo-jong. Photograph: HANDOUT/Reuters

Vietnam’s foreign ministry announced on Saturday that Kim would pay an official goodwill visit to the country “in the coming days” in response to an invitation by the president Nguyễn Phú Trọng, who is also the general secretary of Vietnam’s ruling Communist party.

In his meeting with Trump, Kim is expected to seek a US commitment for improved bilateral relations and partial sanctions relief while trying to minimise any concessions on his nuclear facilities and weapons.

Kim wants to leverage his nuclear and missile programme for economic and security benefits, but doubts remains as to whether he is prepared to deal away an arsenal that he may see as his strongest guarantee of survival.

Last year, North Korea suspended its nuclear and long-range missile tests and unilaterally dismantled its nuclear testing ground and parts of a rocket launch facility without the presence of outside experts. None of those steps were seen as meaningful cutbacks to the North’s weapons capability.

While North Korea has repeatedly demanded that the US take corresponding measures, including sanctions relief, Washington has called for more concrete steps from Pyongyang toward denuclearisation.

Hanoi has been gearing up for the summit with heightened security. Officials say the colonial-era government guest house in central Hanoi is expected to be the venue for the Trump-Kim meeting, with the nearby Metropole hotel as a backup. Streets around the two buildings have been decorated with flowers and the flags of North Korea, the US and Vietnam. Workers were also putting final touches on the International Media Centre.

Vietnam’s foreign ministry says 2,600 members of the foreign press have registered for the event. A traffic ban along Kim’s possible arrival route has also been announced.

The Communist party’s Nhân Dân newspaper on Friday quoted the department of roads as saying the ban would first apply to trucks 10 tons or bigger, and vehicles with nine seats or more on the 170km (105-mile) stretch of highway from Đồng Đăng, the border town with China, to Hanoi from 7pm on Monday to 2pm on Tuesday, followed by a complete ban on Tuesday on all vehicles from 6am to 2pm.

The people’s committee in Lạng Sơn province, where the Đồng Đăng railway station is located, issued a statement on Friday instructing the road operator to clean the highway stretch and suspend road works, among other things, from 24-28 February as “a political task”.