South Korea to work with U.S., North Korea after failed nuclear talks

(Adds U.S. Secretary of State Pompeo's call with China's top diplomat, paragraph 13)

* Trump-Kim talks end without deal on nuclear weapons, sanctions

* N.Korea media hails constructive and sincere exchange between leaders

* All sides see opportunity for more talks

* S.Korea's Moon says to encourage both sides to push on

By Joyce Lee and Hyonhee Shin

SEOUL/HANOI, March 1 (Reuters) - South Korea will work with the United States and North Korea to help them reach a denuclearisation deal, South Korean President Moon Jae-in said on Friday, a day after a U.S.-North Korean summit collapsed over a disagreement on sanctions.

The second meeting between U.S. President Donald Trump and North Korean leader Kim Jong Un, in Vietnam, was cut short after they failed to reach a deal on the extent of sanctions relief North Korea would get in exchange for steps to give up its nuclear programme.

Moon has been active in efforts to end confrontation on the Korean peninsula, meeting Kim three times last year and trying to facilitate his nuclear negotiations with the United States.

"My administration will closely communicate and cooperate with the United States and North Korea so as to help their talks reach a complete settlement by any means," Moon said in a speech in Seoul.

Moon also said Seoul would consult Washington on ways to resume joint projects with North Korea, including tourism development at Mount Kumgang and the Kaesong industrial complex, both in North Korea.

Both the United States and North Korea have said they intend to continue talks, but have not said when a next round might take place.

In a move that could encourage more talks, U.S. officials said on Friday the United States and South Korea are expected to announce that they will not carry out large-scale spring joint military exercises, replacing them with smaller-scale drills.

The allies suspended a number of military drills before and after the first Trump-Kim summit last year to encourage talks with North Korea, which denounced the exercises as training for invasion.

Trump has repeatedly complained about the expense of the exercises and did so again after the Hanoi summit.

Trump and Kim first met in Singapore last June and agreed to establish new relations and peace in exchange for a North Korean pledge to work toward complete denuclearisation of the Korean peninsula.

Trump said two days of talks in Hanoi made good progress but it was important not to rush into a bad deal. He said he had walked away because of unacceptable North Korean demands.

"Basically, they wanted the sanctions lifted in their entirety, and we couldn't do that," he said.