Talks could fail or bring 'greatest deal': Trump

US President Donald Trump said on Saturday his planned meeting with North Korean leader Kim Jong Un could fizzle without an agreement or it could result in "the greatest deal for the world" to ease nuclear tensions between the two countries.

"I may leave fast" if progress does not seem possible, Trump said at a campaign rally for Republican congressional candidate Rick Saccone in western Pennsylvania. Trump said he believes North Korea wants to make peace and that, "I think it's time."

A time and place to meet has not yet been set, although the meeting is supposed to happen by the end of May.

"Who knows what's going to happen?" said Trump, who added that if the meeting takes place, "I may leave fast or we may sit down and make the greatest deal for the world."

Trump made the shocking decision on Thursday to meet with Kim after the North Korean leader's invitation was relayed by a South Korean delegation who visited the White House. The move abruptly reversed decades of US policy aimed at preventing North Korea from developing nuclear weapons and ballistic missiles.

Earlier in Washington, Trump sought to rally international support for a potential summit, saying North Korea had agreed to not conduct another missile test until after proposed meetings had taken place.

"North Korea has not conducted a Missile Test since November 28, 2017 and has promised not to do so through our meetings. I believe they will honor that commitment!" Trump wrote on Twitter.

Trump's comments aligned with what a South Korean official stated on Thursday about the possible talks. Trump's tweet made no mention of nuclear tests, however.

He also boasted that his reducing the North Korean nuclear threat helped save the Winter Olympics that were held last month in South Korea, reported AFP.

Meanwhile, two senior South Korean officials who met with North Korea's Kim Jong Un last week will split up to visit the leaders of China and Japan this week to update them on the talks, a South Korean presidential official said yesterday.

Blue House spokesman Kim Eui-kyeom said in a mobile message that National Security Office head Chung Eui-yong will meet with China's Xi Jinping today, while spy agency chief Suh Hoon, accompanied by one of Chung's deputies Nam Gwan-pyo, will speak with Japan's Shinzo Abe tomorrow, reported Reuters.

Chung and Suh will leave for China and Japan separately today to discuss their visit to North Korea with officials there. Chung is also scheduled to visit Russia after his trip to Beijing, but the details of that have yet to be announced.

The two officials yesterday returned from a visit to the United States where an invitation from North Korean leader Kim Jong Un for dialogue on his nuclear programme was delivered to US President Donald Trump.

Trump's sudden decision to meet with Kim stunned even people in his own administration.

"The expectation is that the talks would lead to a discussion around a conclusion that we're ready to engage in negotiations," a senior State Department official said on Friday.

Some US officials and experts worry North Korea could buy time to build up and refine its nuclear arsenal if it drags out talks with Washington.