China said on Friday tension over North Korea had to be stopped from reaching an "irreversible and unmanageable stage" as a U.S. aircraft carrier group steamed towards the region amid fears the North may conduct a sixth nuclear weapons test.

North Korean Leader Kim Jong Un observes a target-striking contest by the Korean People's Army (KPA) in this undated photo, released by North Korea's Korean Central News Agency (KCNA), April 13, 2017.

Concerns have grown since the U.S. Navy fired 59 Tomahawk missiles at a Syrian airfield last week in response to a deadly gas attack, raising questions about U.S. President Donald Trump's plans for North Korea, which has conducted missile and nuclear tests in defiance of U.N. and unilateral sanctions.

The United States has warned that a policy of "strategic patience" is over. U.S. Vice President Mike Pence travels to South Korea on Sunday on a long-planned 10-day trip to Asia.

China, North Korea's sole major ally and neighbour which nevertheless opposes its weapons programme , has called for talks leading to a peaceful resolution and the denuclearisation of the Korean peninsula.

"We call on all parties to refrain from provoking and threatening each other, whether in words or actions, and not let the situation get to an irreversible and unmanageable stage," Chinese Foreign Minister Wang Yi told reporters in Beijing.

"Force cannot solve the problem, dialogue can be the only channel to resolve the problem."

North Korea for its part denounced the United States for bringing "huge nuclear strategic assets" to the region.

A spokesman for the North Korean Foreign Ministry's Institute for Disarmament and Peace issued a statement condemning the United States for its attack on the Syrian airfield.

"The U.S. introduces into the Korean peninsula, the world's biggest hotspot, huge nuclear strategic assets, seriously threatening peace and security of the peninsula and pushing the situation there to the brink of a war," the North's KCNA news agency said on Friday, citing the statement.

"This has created a dangerous situation in which a thermo-nuclear war may break out any moment." North Korea, still technically at war with the South after their 1950-53