China has urged the United States (US) and North Korea to “hit the brakes” on threatening words and work toward a peaceful resolution of their tense standoff created by Pyongyang's recent missile tests and threats to fire them toward Guam.

The dispute has also raised fears in South Korea, where a conservative political party on Wednesday called for the US to bring back tactical nuclear weapons to the Korean Peninsula.

In a sign of growing concern on the part of Pyongyang's only major ally, Chinese Foreign Minister Wang Yi said in a phone conversation with his Russian counterpart, Sergey Lavrov, that the two countries should work together to contain tensions and permit no one to “stir up an incident on their doorstep,” according to a statement posted on the Chinese foreign ministry's website.

“The most important task at hand is for the US and North Korea to hit the brakes on their mutual needling of each other with words and actions, to lower the temperature of the tense situation and prevent the emergence of an August crisis,” Wang was quoted as saying in the Tuesday conversation.

The ministry quoted Lavrov as saying tensions could rise again with the US and South Korea set to launch large-scale military exercises on August 21.

“A resolution of the North Korea nuclear issue by military force is completely unacceptable and the peninsula's nuclear issue must be peacefully resolved by political and diplomatic methods,” Lavrov was quoted as saying.

China is North Korea's main economic partner and political backer, although relations between Beijing and Pyongyang have deteriorated amid the North's continuing defiance of China's calls for restraint.

In recent months, China has joined with Russia in calling for the US to suspend annual military drills with South Korea in exchange for Pyongyang halting its missile and nuclear tests as a first step toward direct talks.

On Wednesday, the chairman of the US Joint Chiefs of Staff, Marine Corps Gen Joseph Dunford, continued a visit to China following talks the day before with his Chinese counterpart that touched on North Korea. No details of the talks have been released.

Dunford on Tuesday told Fang Fenghui, chief of the People's Liberation Army's joint staff department, that the sides had “many difficult issues” between them but were willing to deal with them through dialogue.

On Monday, Dunford was in Seoul to meet with senior South Korean military and political officials and the local media, seeking to ease anxiety while showing his willingness to back President Donald Trump's warnings if need be.

The US wants to peacefully resolve tensions with North Korea, but Washington is also ready to use the “full range” of its military capabilities, Dunford said.

His visit to Asia, which also will include a stop in Japan, comes after Trump last week declared the US military “locked and loaded” and said he was ready to unleash “fire and fury” if North Korea continued to threaten the United States.

North Korea's military on Tuesday presented leader Kim Jong Un with plans to launch missiles into waters near the US territory of Guam and “wring the windpipes of the Yankees,” even as both Koreas and America signalled their willingness to avert a deepening crisis, with each suggesting a path toward negotiations.

The tentative interest in diplomacy follows unusually combative threats between Trump and North Korea amid worries Pyongyang is nearing its long-sought goal of being able to send a nuclear missile to the US mainland.

Next week's start of US-South Korean military exercises that enrage the North each year could make diplomacy even more difficult.

North Korea's threats against Guam and its advancing missile capabilities, highlighted by a pair of intercontinental ballistic missile (ICBM) flight tests in July, have raised concern in South Korea, where some believe a fully functional ICBM in Pyongyang would undermine the alliance between Washington and Seoul.

This has led to growing calls among South Korean conservatives for the United States to redeploy tactical nuclear weapons in South Korea after withdrawing them in the 1990s. The opposition Liberty Korea Party on Wednesday adopted the demand as its official party line, saying that the presence of such weapons would strengthen deterrence against the North.

During an inspection of the North Korean army's Strategic Forces, which handles the missile programme, Kim praised the military for drawing up a “close and careful plan” and said he would watch the “foolish and stupid conduct of the Yankees” a little more before deciding whether to order the missile test, the state-run Korean Central News Agency said.

Kim appeared in photos sitting at a table with a large map marked by a straight line between what appeared to be northeastern North Korea and Guam, and passing over Japan apparently showing the missiles' flight route.

The missile plans were previously announced. Kim said North Korea would conduct the launches if the “Yankees persist in their extremely dangerous reckless actions on the Korean Peninsula and its vicinity,” warning the United States to “think reasonably and judge properly” to avoid shaming itself, the news agency said.

US Secretary of State Rex Tillerson told reporters in Washington on Tuesday, “We continue to be interested in trying to find a way to get to dialogue, but that's up to (Kim)”.

Lobbing missiles toward Guam, a major US military hub in the Pacific, would be deeply provocative from the US perspective. A miscalculation on either side could lead to military confrontation.

South Korean President Moon Jae-in, meanwhile, a liberal who favours diplomacy, urged North Korea to stop provocations and to commit to talks over its nuclear weapons programme.

Moon, in a televised speech yesterday, on the anniversary of World War II's end and the Korean Peninsula's liberation from Japanese colonial rule, said Seoul and Washington agree that the nuclear standoff should “absolutely be solved peacefully.”

He said no US military action on the Korean Peninsula could be taken without Seoul's consent.

North Korea's military said last week that it would finalise the plan to fire four ballistic missiles near Guam, which is about 3,200 kilometres from Pyongyang.

It would be a test of the Hwasong-12, a new missile the country flight-tested for the first time in May.

The liquid-fuel missile is designed to be fired from road mobile launchers and has been described by North Korea as built for attacking Alaska and Hawaii.