The plan to modernize North Korea's outdated railways and roads and connect them with the South was among many agreements reached between North Korean leader Kim Jong Un and South Korean President Moon Jae-in, who met three times this year as part of a diplomatic push that eased tensions over the North's nuclear program.
"We're getting along very well", Trump told reporters aboard Air Force One on his return from Argentina.
A United States think tank said last month it had identified at least 13 of an estimated 20 active, undeclared missile bases inside North Korea, underscoring the challenge for American negotiators hoping to persuade Kim to give up his weapons programs.
But despite several rounds of negotiations between leaders and diplomats from North and South Korea and the USA, there is still no clear timetable for when much of this will happen, and few concrete signs of progress.
Last month at a press conference, Trump had expressed hope that he would meet Kim early next year. This reports the South Korean news agency "Yonhap", citing the army leadership in Seoul.
However, she added that Trump and Moon agreed that "vigorous sanctions" need to be maintained so that North Korea understands that denuclearisation is the only option.
"President Trump discussed his intention to have a second US-DPRK summit", Sanders said, and the two leaders "restated their commitment to closely coordinate on next steps". The incident did not trigger any gunfire, unlike previous year when a North Korean soldier ran across under a hail of bullets from his own side.
Complications: The Washington Post reported that in order for the trip to happen, South Korea had to receive special permission from the United Nations due to sanctions that are now in place on North Korea.
A South Korean train with a sign reading "Seoul to Sinuiju" crossed into the North, Friday, for a long-stalled joint inspection of railway sections there.
They have begun work to reconnect their railway systems, removed landmines and destroyed military bunkers at parts of the frontier. Kim agreed to travel to Seoul after hosting Moon in Pyongyang in September for their third summit this year.
But prospects of a fourth Moon-Kim meeting have recently dimmed, with negotiations on denuclearizing the North grinding to a halt. "We have a good relationship". But beyond surveys and tape-cuttings, the Koreas can not move much further along without the removal of US -led sanctions against the North, which isn't likely before it takes firmer steps toward relinquishing its nuclear weapons and missiles.