WASHINGTON, U.S. President Donald Trump urged Russian President Vladimir Putin on Friday to help keep pressure on North Korea until it dismantles its nuclear weapons program, Trump's spokeswoman said.

The two leaders spoke by phone and discussed nuclear agreements, trade, and the political situations in North Korea, Ukraine and Venezuela, according to White House press secretary Sarah Sanders.

"They spoke about North Korea for a good bit of time on the call and reiterated both the commitment and the need for denuclearization," Sanders told reporters at the White House.

"And the president said several times on this front as well the need and importance of Russia stepping up and continuing to help and put pressure on North Korea to denuclearize," she said. "And that was again the focus of the president's comment on that front."

Putin held his first summit with North Korean leader Kim Jong-un in Russia's Vladivostok last month.

The meeting was widely regarded as part of North Korea's push to secure sanctions relief from other major powers following the breakdown of the second Trump-Kim summit in Vietnam in February.

Washington has demanded Pyongyang's total surrender of its nuclear and ballistic missile programs, while the North has asked for sanctions relief as a confidence-building measure.

Trump noted his phone call with Putin in a tweet.

"We discussed Trade, Venezuela, Ukraine, North Korea, Nuclear Arms Control and even the 'Russian Hoax,'" he wrote. "Very productive talk!"

Putin has suggested reviving six-party talks on North Korea's denuclearization to break the impasse in U.S.-North Korea talks.

The multilateral forum involved the two Koreas, the U.S., China, Japan and Russia before it collapsed in 2009.

"I think it's not just what our preference is," U.S. National Security Adviser John Bolton said in an interview with Fox News Sunday.

"I think Kim Jong-un, at least up until now, has wanted the one-on-one contact with the United States, which is what he has gotten," he said.

Source: Yonhap news Agency