US DEFENCE Secretary James Mattis said yesterday that Washington’s military might would bolster diplomacy in the stand-off with North Korea.

Speaking to US troops at the Panmunjom “peace village” in the heavily fortified Demilitarised Zone between North and South Korea, he said: “We're doing everything we can to solve this diplomatically.

“Ultimately, our diplomats have to be backed up by strong soldiers and sailors, airmen and marines,” he added, “so they speak from a position of strength, of combined strength, of alliance strength, shoulder to shoulder.”

The US has so far rejected a Chinese-Russian proposal to return to six-nation denuclearisation talks, which have been stalled since 2009.

Meanwhile, a naval exercise involving three US aircraft carrier strike groups are being planned for next month in the Asia-Pacific, a US official said.

The war game is planned to coincide with  US President Donald Trump’s visit to the region, which will include a stop in Seoul.

This week, North Korean UN ambassador Ja Song Nam branded recent joint US-South Korean manoeuvres a rehearsal for “nuclear war.”

In an interview with the RIA Novosti news agency published on Thursday, Russian MP Anton Morozov, a member of the Russian parliament’s international relations committee, accused the US of deliberately undermining efforts to reach a diplomatic solution.

“America is destabilising the situation in the region,” he said. “They want to contain China and other nations.”

Mr Morozov claimed that some in Washington had realised regional stability depended on US withdrawal — even if “leadership would be passed over to Russia and China.”

But he said: “There is no other way out, because any further escalation of tensions could lead to the third world war.”

After returning from a visit to North Korea early this month, Mr Morozov said Pyongyang was preparing for more missile tests and that “their mood is rather belligerent.”

North Korean diplomats have said that the US should take “literally” Pyongyang’s  threat to test a hydrogen bomb over the Pacific Ocean.

“The US is talking about a military option and even practising military moves,” Ri Yong Pil said. “They’re pressuring us on all fronts with sanctions. If you think this will lead to diplomacy, you’re deeply mistaken.”