China responded to US President Donald Trump's apocalyptic "fire and fury" threat against North Korea by pointedly warning on Wednesday against any rhetoric that could inflame tensions over Pyongyang's weapons programmes.

Calling the situation on the Korean Peninsula "complicated and sensitive", China's foreign ministry issued a statement warning that parties involved in the impasse should avoid "words and actions that escalate the situation".

The ministry had been asked to respond to Trump's comment on Tuesday that North Korea would "be met with fire and fury like the world has never seen" if it did not refrain from further bellicose threats against the United States.

Trump's warning came as Pyongyang said it was considering a missile strike near the US territory of Guam and after US media reported North Korea may have successfully miniaturized a nuclear warhead, considered a key step in becoming a full nuclear power.

Trump's words marked a sharp intensification of Washington's rhetoric over the North's nuclear and missile programmes, which saw a seventh set of United Nations sanctions imposed on it at the weekend, and appeared to echo Pyongyang's own trademark threats.

Trump's tone was markedly different to Secretary of State Rex Tillerson's assurances last week that Washington was not seeking regime change in Pyongyang.

North Korea raised the stakes just hours after Trump's warning, saying it was considering missile strikes near US strategic military installations on the Pacific island of Guam.

Once finalised, the plan could be put into action at "any moment" once leader Kim Jong-Un made a decision, the official Korean Central News Agency (KCNA) quoted a military statement as saying.

China, Pyongyang's traditional ally and biggest trading partner, has long called for the United States and North Korea to exercise restraint in the impasse and seek a negotiated solution that would de-nuclearise its secretive neighbour.