China is urging all parties in the Korean standoff to stay calm and "stop irritating each other", as North Korea says the United States is pushing the region to the brink of nuclear war.
North Korea's state media published a rare, strong criticism of China on Wednesday, saying Chinese state media commentaries calling for tougher sanctions over Pyongyang's nuclear program were undermining relations with Beijing and worsening tensions.
The United States has urged China, North Korea's only major ally, to do more to rein in its neighbour's nuclear and missile programs, which have prompted an assertive response from the Trump administration, warning that an "era of strategic patience" is over.
US Secretary of State Rex Tillerson said on Wednesday Washington was working on more sanctions targeting North Korea if Pyongyang takes steps that merit a new response.
Mr Tillerson said last week that China had said it had warned Pyongyang it would impose sanctions of its own if North Korea carried out another nuclear test.
The United States has sent a nuclear-powered aircraft carrier to Korean waters and a pair of strategic US bombers flew training drills with South Korean and Japan in another show of strength this week.
Chinese Foreign Ministry spokesman Geng Shuang called the situation "highly complex" and sensitive.
"The urgent task is to lower temperatures and resume talks," he told reporters.
"We again urge all relevant parties to remain calm and exercise restraint, stop irritating each other, work hard to create an atmosphere for contact and dialogue between all sides, and seek a return to the correct path of dialogue and negotiation as soon as possible."
The bomber flights coincided with US President Donald Trump raising eyebrows when he said he would be "honoured" to meet North Korean leader Kim Jong-un in the right circumstances, and as his CIA director landed in South Korea for talks.
North Korea said the bombers conducted "a nuclear bomb dropping drill against major objects" in its territory at a time when Mr Trump and "other US warmongers are crying out for making a pre-emptive nuclear strike".
"The reckless military provocation is pushing the situation on the Korean peninsula closer to the brink of nuclear war," North Korea's official KCNA news agency said.
Tension on the Korean peninsula has been high for weeks, driven by concern that North Korea might conduct its sixth nuclear test in defiance of UN Security Council resolutions.