UPDATE 1-Trump says he spoke to South Korean president about U.N. sanctions on N. Korea

on N. Korea@ (Adds background on vote on sanctions, ASEAN meetings)

BEDMINSTER, N.J., Aug 6 (Reuters) - U.S. President Donald Trump said he had spoken with South Korean President Moon Jae-in on Sunday, a day after the U.N. Security Council backed new sanctions on North Korea over its intercontinental ballistic missile tests.

"Just completed call with President Moon of South Korea. Very happy and impressed with 15-0 United Nations vote on North Korea sanctions," Trump said in a Twitter post.

The new sanctions on Pyongyang could slash North Korea's $3 billion annual export revenue by a third. North Korea has been a focus of international attention in recent months, as it has conducted a series of ballistic missile tests, including two in July that helped prompt the U.N. action.

The U.S.-drafted resolution bans North Korean exports of coal, iron, iron ore, lead, lead ore and seafood. It also prohibits countries from increasing the current numbers of North Korean laborers working abroad, bans new joint ventures with North Korea and any new investment in current joint ventures.

Washington has threatened to exert trade pressure on Beijing and impose sanctions on Chinese firms doing business with Pyongyang. Last week, Trump signed into law a sweeping set of sanctions on North Korea that targeted foreign firms, including Chinese banks, that do business with the reclusive kingdom and countries that hire its workers.

China's foreign minister said on Sunday new U.N. sanctions on North Korea were the right response to a series of missile tests, but dialogue was vital to resolve a complex and sensitive issue, now at a "critical juncture."

North Korea has been under U.N. sanctions since 2006. The new measures, which expand the existing sanctions, were a response to five nuclear tests and four long-range missile launches.

The standoff is expected to dominate Monday's ASEAN Regional Forum, a gathering of 27 foreign ministers, including former participants in halted six-party talks on North Korea - Russia, Japan, the United States, China and North and South Korea. (Reporting by Patricia Zengerle and David Shepardson in Washington and Amy Tennery in Bedminister, N.J.; editing by Diane Craft)