WASHINGTON - US President Donald Trump said he is hopeful about his forthcoming meeting with Kim Jong-un, top leader of the Democratic People's Republic of Korea (DPRK), while warning about the consequences if the meeting did not go well.

"I hope to have a very successful meeting," Trump said at a joint news conference with Japanese Prime Minister Shinzo Abe in Florida on Wednesday, referring to his planned meeting with Kim scheduled in May or early June. "We will be doing everything possible to make it a worldwide success."

Yet, Trump made clear that he'd still be ready to pull out of what he called a "tremendous" meeting between the leaders of two countries that have been longtime adversaries.

"If I think that it's a meeting that is not going to be fruitful, we're not going to go," said the US president.

"If the meeting, when I'm there, is not fruitful, I will respectfully leave the meeting, and we'll continue what we're doing or whatever it is that we'll continue," he added.

Washington and Pyongyang have started direct negotiations about the two leaders' meeting. Trump said that CIA chief Mike Pompeo has formed a "good relationship" with Kim in their secret meeting in Pyongyang last week.

Abe was on a two-day visit to the United States starting from Tuesday, the second of its kind since Trump assumed the presidency last year.