Before the summit, there had been fears in the U.S. that Moon's North Korea policies could weaken the united front that the international community needs to present in pressuring North Korea.

Moon was referring to a joint statement with Trump on Friday which said the U.S. president "supported President Moon's aspirations to restart inter-Korean dialogue on issues including humanitarian affairs."

"We have secured the United States' support for us to lead the resolution of the Korean Peninsula problem through dialogue," Moon said on returning to Korea on Sunday. But he added, "We now have to start a long journey to build a structure of lasting peace on the Korean Peninsula."

President Moon Jae-in succeeded in winning support from U.S. President Donald Trump to play a leading role in resuming talks with North Korea during their meeting in Washington on Friday.

A government official here said, "It's true that there were some worries that it may undermine sanctions on North Korea" but the summit dispelled them and laid the groundwork for Moon to push his North Korea policy "with more confidence."

But the two presidents drew clear lines in the sand. They "affirmed their commitment to fully implement existing sanctions and impose new measures designed to apply maximum pressure on North Korea to compel Pyongyang to cease its provocative actions and return to sincere and constructive talks," the statement said.

They also agreed to set up a new "Extended Deterrence Strategy and Consultation Group" to discuss North Korean issues together.

Meanwhile, Moon was also able to win a nod to his aim of transferring full operational control of South Korean troops within his term in office. The statement said the two countries will "work to expeditiously enable the conditions-based transfer of wartime operational control of [South Korean] forces."

But Trump extracted a heavy price. "We are renegotiating a trade deal right now... and hopefully it will be an equitable deal, it will be a fair deal to both parties. It's been a rough deal for the United States, but I think that it will be much different and will be good for both parties," he told reporters.

However, the written joint statement later did not specifically mention the bilateral free trade agreement that went into force in 2012.

There was no mention of the deployment of a Terminal High-Altitude Area Defense battery here, which had stirred up plenty of controversy in the run-up to their meeting.