Trump indefinitely pushed back the end of the two-week truce on Tuesday with Tehran yet to respond but he said a US blockade of Iran's ports would continue.

"The current regional situation stands at a critical juncture transitioning between war and peace; the paramount priority remains to make every effort to prevent a resumption of hostilities," Chinese foreign ministry spokesman Guo Jiakun told a news briefing.

Guo did not comment directly on the ceasefire when asked about it, adding only that Beijing would continue to play a "constructive" role.