US President Donald Trump says that if his planned talks with North Korean leader Kim Jong-un are not fruitful he will "walk out".
At a joint news conference, he and Japanese PM Shinzo Abe said maximum pressure must be maintained on North Korea over nuclear disarmament.
Abe is at the president's Mar-a-Lago resort in Florida for talks.
Earlier, Trump confirmed that CIA Director Mike Pompeo had made a secret trip to North Korea to meet Mr Kim.
He said Pompeo had forged a "good relationship" with Mr Kim - whom the US president was last year calling "little rocket man" - and that the meeting had gone "very smoothly".
Trump is expected to hold a summit with Mr Kim by June. Details, including a location, are still being worked out.
Meanwhile, South Korean president Moon Jae-in is set to meet Kim next week.
Speaking on Thursday, Moon said North Korea had said it was ready for "complete denuclearisation", and called for "bold imagination and creative solutions" to ensure the Koreas summit and the Trump-Kim summit would succeed.
President Trump said at the joint news conference that if he did not think the meeting would be successful he would not go, and if the meeting went ahead but was not productive, he would walk out.
"Our campaign of maximum pressure will continue until North Korea denuclearises," he added.
Media captionHow to talk to North Korea
"As I've said before, there is a bright path available to North Korea when it achieves denuclearisation in a complete and verifiable and irreversible way. It would be a great day for them, it would be a great day for the world."
On trade, Trump and Abe agreed to start talks on "free, fair and reciprocal trade deals".
Trump said the US remained opposed to rejoining the Trans Pacific Partnership unless Japan and other parties to the trade pact offered "a deal that I can't refuse".
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The US president did not exempt Japan from punitive steel and aluminium tariffs, as he has done for other US allies.
Turning to North Korea, Abe said he had urged President Trump to help bring about the release of Japanese citizens kidnapped by North Korea in the 1970s and 1980s.