Construction on ambitious project cannot begin while sanctions over North’s nuclear and missile programmes are in place.

North and South Korea have held a ceremony for an ambitious project to modernise and reconnect rail and road links, although construction cannot begin without progress in nuclear negotiations.

A nine-car special train carrying some 100 South Korean officials, politicians and five people born in the North, left the Seoul railway station early on Wednesday morning for a two-hour journey to the North’s border city of Kaesong.

There, they were joined by a 100-strong North Korean delegation, as well as officials from the United Nations, China, Russia and Mongolia, according to South Korea’s unification ministry.

The United States gave their support for the ceremony, South Korean officials said, but work cannot begin while sanctions block the shipment of energy and metal products, as well as other supplies.

South Korean President Moon Jae-in and the North’s leader Kim Jong-un agreed to hold the ceremony by the end of this year when they met at their third summit in Pyongyang in September.

Concerns arose that the train and other materials being brought into the North for the ceremony could breach various sanctions imposed on the isolated country over its nuclear weapons programme, but the UN Security Council reportedly granted a waiver for the event.

Seoul stressed that the ceremony would not herald the start of actual work on reconnecting and modernising road and rail links between the two Koreas – which remain technically at war after their 1950-1953 conflict ended without a peace treaty.

The event is a mere “expression of a commitment” to the projects, a spokesperson for the South Korean unification ministry said, adding that construction would depend on “progress on the North’s denuclearisation and circumstances concerning sanctions”.

The two sides wrapped up their joint railway and road inspections for the projects this month.

South Korea has set aside some $620,000 for the endeavour.

The ceremony comes as Washington ramps up efforts to convince Pyongyang to give up its nuclear weapons.

Following a rapid rapprochement earlier this year that culminated in an historic summit between Donald Trump and Kim, progress has stalled with both sides accusing each other of dragging their feet and acting in bad faith.

Critics say North Korea has made no concrete commitments and is unlikely to surrender its atomic arsenal, while Washington’s policy of maintaining pressure through isolation and sanctions has left Pyongyang seething.

Trump said on Monday that he was “looking forward” to his second summit with Kim, which Washington says may take place early next year.

He tweeted the statement after he was briefed by Stephen Biegun, the US special representative on North Korea, who wrapped up a three-day trip to Seoul on Saturday.

Biegun said last week Washington will be more lenient in enforcing its blanket ban on US citizens’ travel to the totalitarian state when dealing with aid workers, a goodwill gesture as Trump seeks a fresh summit.

The Trump administration has generally refused to let US aid groups operate in North Korea, seeking to both maximise pressure on Pyongyang and ensure the safety of Americans.

Biegun also said in Seoul last week Washington was willing to discuss trust-building initiatives with Pyongyang.

Senior transport officials from Russia, China and Mongolia as well as several foreign ambassadors to South Korea will attend Wednesday’s ceremony, the South’s Unification Ministry said.