Beijing, China - China said it would defend an international system with the UN "at its core," in an apparent dig at US President Donald Trump's so-called "Board of Peace".

Beijing confirmed on Tuesday that it had received a US invitation to join the board, which presents itself vaguely as aimed at resolving conflicts.

China has yet to confirm whether it will accept the invitation, but foreign ministry spokesman Guo Jiakun told a news conference on Wednesday that Beijing would support a UN-based international world order regardless of "changes".

"No matter how the international situation changes, China firmly upholds the international system with the United Nations at its core... international relations based on the objectives and principles of the UN Charter," Guo said.

China, the world's second-largest economy and a permanent member of the UN Security Council, traditionally defends the international system while calling for reforms.

Under Trump, the US has conversely chipped away at the legitimacy of the UN, along with its ally Israel, accused of committing myriad war crimes and crimes against humanity in its destruction of Gaza – up to and including genocide.

"The UN just hasn't been very helpful," Trump told reporters at the White House during a rambling press conference Tuesday. "I'm a big fan of the UN potential, but it has never lived up to its potential."