Beijing on Thursday expressed hope that the United States and North Korea will keep talking, saying the nuclear issue will not be solved “overnight”, after a much-anticipated summit in Hanoi ended without a deal.

China is Pyongyang’s sole major ally and North Korean leader Kim Jong Un traveled across the neighbouring country by train to his second meeting with US president, Donald Trump, which ended ahead of schedule without any joint announcements.

Chinese foreign ministry spokesman, Lu Kang said he had yet to hear what Trump or the North Korean leader had to say about the meeting.

“But I have always hoped that everyone can realise that the nuclear problem on the Korean peninsula has been going on for many years and that solving this problem is definitely not something that can be achieved overnight,” Lu said at a regular press briefing.

“It is not a very easy process, otherwise it would not have dragged on until today,” Lu said.

Lu reiterated Beijing’s call for Washington and Pyongyang to “take care of each other’s legitimate concerns.”

“I hope that both sides can continue to maintain such a dialogue,” he said.

Kim met with Chinese President Xi Jinping four times in the past year, most recently in January.