Seoul, South Korea (Reuters): North Korea put on a massive live-fire drill on Tuesday to mark the foundation of its military, as a U.S. submarine docked in South Korea in a show of force amid growing concern over Pyongyang's nuclear and missile programs, media reports said.

The port call by the USS Michigan came as a U.S. aircraft carrier strike group steams for Korean waters and as the top nuclear envoys from South Korea , Japan, and the United States met in Tokyo to discuss the North's refusal to give up its nuclear program.

Fears have risen in recent weeks that North Korea could soon conduct another nuclear test or long-range missile launch in defiance of United Nations sanctions.

South Korea 's Yonhap News Agency reported that the North appeared to have deployed a large number of long-range artillery units in the region of Wonsan on its east coast on Tuesday, conducting a large-scale, live-fire drill .

The report, citing an unidentified government source, said the live-fire exercise was possibly supervised by North Korean leader Kim Jong Un.

While South Korea 's Defence Ministry could not immediately confirm the report, the Office of the Joint Chiefs of Staff said: "Our military is closely monitoring the North Korean military's movement in Wonsan areas and we are firmly maintaining readiness."

North Korea defiantly said in a state media commentary marking the 85th anniversary of the foundation of the Korean People's Army's that its military was prepared "to bring to closure the history of U.S. scheming and nuclear blackmail".

The official Rodong Sinmun newspaper said in a front-page editorial, "There is no limit to the strike power of the People's Army armed with our style of cutting-edge military equipment including various precision and miniaturized nuclear weapons and submarine-launched ballistic missiles."

South Korea 's Navy said it was conducting a live-fire exercise with U.S. Navy destroyers on Tuesday in waters west of the Korean peninsula and would soon join the USS Carl Vinson aircraft carrier strike group approaching the region.

The carrier group was sent to the region as a warning to North Korea and a show of solidarity with U.S. allies.

Japan's Chief Cabinet Secretary, Yoshide Suga, told a media briefing that China's nuclear envoy, Wu Dawei, would hold talks with Japanese Foreign Ministry officials on Tuesday. A ministry source said Wu was likely to meet his Japanese nuclear counterpart on Wednesday.

The U.S. envoy for North Korea policy, Joseph Yun, said, "As we discuss these things all our steps and every part of them will be in coordination and consultation with our partners."

"We believe China has a very, very important role to play," Yun said.

 

Rare Senate Briefing

Matching the flurry of diplomatic and military activity in North Asia, the State Department in Washington said on Monday U.S. Secretary of State Rex Tillerson would chair a special ministerial meeting of the U.N. Security Council on North Korea on Friday.

Tillerson, along with Defense Secretary Jim Mattis, Director of National Intelligence Dan Coats and Joint Chiefs chairman General Joseph Dunford, would also hold a rare briefing for the entire U.S. Senate on North Korea on Wednesday, Senate aides said.

On Monday, U.S. President Donald Trump called for tougher new U.N. sanctions on Pyongyang, saying the North was a global threat and "a problem that we have to finally solve".

"The status quo in North Korea is also unacceptable," Trump told a meeting with the 15 U.N. Security Council ambassadors, including China and Russia, at the White House. "The council must be prepared to impose additional and stronger sanctions on North Korean nuclear and ballistic missile programs."

The official China Daily said on Tuesday it was time for Pyongyang and Washington to take a step back from harsh rhetoric and heed the voices of reason calling for a peaceful resolution.

"Judging from their recent words and deeds, policymakers in Pyongyang have seriously misread the U.N. sanctions, which are aimed at its nuclear/missile provocations, not its system or leadership," the newspaper said in an editorial.

"They are at once perilously overestimating their own strength and underestimating the hazards they are brewing for themselves," it said.

In a phone conversation with Trump on Monday, Chinese President Xi Jinping called for all sides to exercise restraint.

As the carrier group drills continued, the USS Michigan arrived in the South Korean port of Busan on Tuesday, the U.S. Navy said. The nuclear-powered submarine is built to carry and launch ballistic missiles and Tomahawk cruise missiles.

As well as his military show of force, Trump has also sought to pressure China to do more to rein in its nuclear-armed neighbor.

China, North Korea 's sole major ally, has in turn been angered by Pyongyang's belligerence, as well as its nuclear and missile programs.

Angered by the approach of the carrier group, which could arrive within days, North Korea said the deployment of the USS Carl Vinson was "an extremely dangerous act by those who plan a nuclear war to invade".