State Councilor Yang Jiechi talked with US Secretary of State Rex Tillerson on Thursday over the phone about the Iran nuclear issue ahead of an announcement that US President Donald Trump is expected to make about a 2015 nuclear deal.

According to US State Department spokeswoman Heather Nauert, Tillerson also spoke to French and Russian foreign ministers on the same day and to British Foreign Secretary Boris Johnson "in recent days".

Foreign Ministry spokeswoman Hua Chunying on Friday reiterated China's position on the issue, calling all the parties to continue upholding and implementing the deal.

"We believe the deal has played an important role in ensuring the international nonproliferation regime and maintaining peace and stability in the Middle East," Hua told a news conference.

During a White House speech set for early Saturday morning Beijing time, Trump is expected to declare that the 2015 deal is no longer in the US national interest.

Officials say he will not kill the international accord outright, instead "decertifying" the agreement and leaving US lawmakers to decide its fate.

Under the deal, sanctions on Iran would be lifted in exchange for Iran limiting its nuclear programs.

The likely move has drawn concerns from other signatories of the deal: Britain, France, Russia, China and Germany all voiced support for maintaining the deal.

In the conversation with Tillerson on Thursday, Russian Foreign Minister Sergey Lavrov said that Teheran is abiding by its commitments and emphasized the need for other co-authors to adhere to the plan, according to the Russian Foreign Ministry.

Wu Sike, China's former special envoy to the Middle East, said the hard-won deal is an important outcome that has gained acknowledgment from the international community, and it is "unreasonable" for the US to quit, since it will lead to increased tensions in the Middle East and "likely trigger new competition in the region".

Agencies and Zhou Jin contributed to this story.