South Korean President Moon Jae-in said U.S. President Donald Trump deserves a Nobel Peace Prize for his efforts to end the standoff with North Korea over its nuclear weapons program, a South Korean official said on Monday.

“President Trump should win the Nobel Peace Prize. What we need is only peace,” Moon told a meeting of senior secretaries, according to a presidential Blue House official who briefed media.

Moon and North Korean leader Kim Jong Un on Friday pledged to end hostilities between the two countries and work towards the “complete denuclearization” of the Korean peninsula in the first inter-Korean summit in more than a decade.

Trump is preparing for his own summit with Kim, which he said would take place in the next three to four weeks.

That upcoming meeting was the main subject of a private walk and chat that Kim and Moon had during their meeting at the border, the official said.

In January, Moon said Trump “deserves big credit for bringing about the inter-Korean talks. It could be a resulting work of the U.S.-led sanctions and pressure”.

Moon’s Nobel Prize comment came in response to a congratulatory message from Lee Hee-ho, the widow of late South Korean President Kim Dae-jung, in which she said Moon deserved to win the prize in recognition of his efforts, the Blue House official said.

Moon responded by saying Trump should get it.

Kim Dae-jung championed the so-called Sunshine policy of engagement with North Korea, and won the 2000 Nobel Peace Prize after engineering the first inter-Korean summit with former North Korean leader Kim Jong Il.

During Monday’s meeting, Moon called for a joint study with the North of economic projects that could be resumed without violating international sanctions imposed on North Korea for its nuclear weapons and ballistic missile programs.

“The study is to set in motion the programs that are not subject to sanctions, while exploring what the two Koreas could do when the sanctions are lifted in the future,” the official quoted Moon as saying.

The Trump administration has led a global effort to impose ever stricter sanctions on North Korea.

U.S. Secretary of State Mike Pompeo said on Sunday that Trump would maintain a “pressure campaign” of harsh sanctions on impoverished North Korea until Kim scraps his nuclear weapon program.

Late Saturday, Trump told Moon in a phone call that he was pleased the leaders of the two Koreas reaffirmed the goal of complete denuclearisation during their summit, South Korean officials said on Sunday.

The White House said Trump and Moon had “emphasized that a peaceful and prosperous future for North Korea is contingent upon its complete, verifiable, and irreversible denuclearization”.

A senior adviser to Moon told Reuters last week that the South Korean government had a “comprehensive roadmap” that it was sharing with the United States ahead of Trump’s meeting with Kim.