North Korea's state media has threatened to turn the USA mainland into "ashes" with its "super-mighty preemptive strike" as the nuclear stand-off between Washington and the reclusive state continues. The US, along with South Korea, should suspend annual military exercises that antagonize North Korea in exchange for Pyongyang halting its nuclear program, China's Foreign Minister Wang Yi said in early March.

Mr Pence made the unannounced visit at the start of his 10-day trip to Asia in a United States show of force that allowed the Vice President to gaze at North Korean soldiers from afar and stare directly across a border marked by razor wire.

Trump last week had said that he had sent an "armada" to the Korean peninsula.

The Yomiuri ShimbunPrime Minister Shinzo Abe praised the U.S. stance of strengthening pressure on North Korea during a meeting with U.S. Vice President Mike Pence on Tuesday and once again stressed the unity of Japan and the United States.

But Sen. Lindsey Graham (R-S.C.) said Wednesday that he'd personally advised Trump be more blunt with Beijing, asking the President to "tell China that if you don't take care of it, we will".

He said that an "all-out war" would result if the USA took military action.

Beijing has denied any political motive behind the cancellation of flights to Pyongyang, amid speculations that the move was meant to pressure North Korea over its missile program.

More news: North Korea attempts but fails to launch missile - South Korea

At the United Nations on Monday, North Korea's permanent representative Ambassador Kim In-ryong, condemned the U.S. missile strikes in Syria, which targeted an air base after a suspected chemical attack by the government.

Pence also said the USA would protect freedom of navigation in the South China Sea, the sea lanes vital to global shipping where China has been staking claim to disputed territory.

North Korea has conducted several missile and nuclear tests in defiance of United Nations sanctions and has said it has developed a missile that can strike the U.S. mainland.

China has pledged to build an "indestructible combat force" in a major military reshuffle of 84 units at a time of huge global tension over North Korea.

US President Donald Trump made an offer to Chinese President Xi Jinping that there will be better trade terms between the two if China puts North Korea's threatening behaviour to rest.

Meanwhile, U.S. Vice-President Mike Pence has warned Pyongyang against testing Trump's "resolve" and declared an end to Obama's "strategic patience" policy. These words have been brought up repeatedly when it comes to dealing with North Korea since the Trump administration came into office. "We obviously don't have the military might that the United States does", he said.

Nevertheless, the US reportedly directed two additional aircraft carrier groups toward the Korean Peninsula this week.