Xi praised the "positive aspiration" of President Donald Trump to achieve a political settlement of the Korean peninsula issue after the US leader agreed to meet Kim Jong Un, state news agency Xinhua added.

"I hope the United States and North Korea can start to get in touch and dialogue as soon as possible, and strive to obtain positive achievements," said Xi, according to Xinhua.

Trump Thursday agreed to a historic meeting with Kim -- the first ever meeting between a US president and a North Korean leader -- by May, in a stunning development in America's high-stakes nuclear standoff with North Korea.

Xi told Trump the move to pursue denuclearisation through "the right track of dialogue" was positive.

It comes after the South's envoy who returned from the North earlier this week said Pyongyang had offered to hold denuclearisation talks in return for security guarantees.

The North also agreed to hold a historic summit between its leader Kim Jong Un and South Korean President Moon Jae-in in late April.

Envoy Chung Eui-yong, head of Seoul's National Security Office, will travel to China as well as Russia following his Washington trip where he announced Trump will meet Kim.

Under pressure from US President Donald Trump, Beijing has backed a series of United Nations sanctions against North Korea, sending relations between the Cold War-era allies to a new low.

Beijing has repeatedly called for negotiations to peacefully put an end to tensions that have raised fears of nuclear warfare, after months of fiery rhetoric between Kim and Trump.

Xi told Trump China would "firmly devote itself to achieve the denuclearisation of the Korean peninsula", and to solving the problem through dialogue and consultation, Xinhua said.

But China's foreign minister Thursday stressed that "the sincerity" of all parties to solve the nuclear crisis would be tested, noting that breakthroughs on the North Korean nuclear issue had collapsed in the past.

"Of course it takes more than one cold day to freeze three feet of ice," he said.

The thaw follows a period of extreme tension between Washington and Pyongyang that sounded like the growing drumbeat of war.