French President Emmanuel Macron on Wednesday said he did not know whether US President Donald Trump would stick to the 2015 Iran nuclear deal that many in the West see as the best hope of preventing Teheran from getting a nuclear bomb.

Macron, followed by German Chancellor Angela Merkel, visited Washington last week in the hope of persuading Trump not to reimpose sanctions on Iran before a May 12 deadline and imperil the 2015 deal but the White House has sounded unconvinced.

Under the accord, Teheran agreed to limit its nuclear program in return for relief from US and other economic sanctions. The deal was struck by Britain, China, France, Germany, Russia, the United States and Iran.

"I don't know what the US president will decide on May 12," Macron told reporters in Sydney after meeting Prime Minister Malcolm Turnbull. The White House said on Tuesday that the Iran deal was made on "false pretense" in 2015, Xinhua News Agency reported.

"Iran's nuclear capability were far more advanced and far further along than they ever indicated," said White House Press Secretary Sarah Sanders at a daily briefing.

"The deal that was made on things that weren't accurate. And we have a big problem with that," Sanders added.

Macron said he had pushed the idea of a much broader Iran agreement with Trump, which was received "very positively".

"I just want to say whatever the decision will be, we will have to prepare such a broader negotiation and a broader deal because I think nobody wants a war in the region, and nobody wants an escalation in terms of tension in the region," Macron added.

China reiterated on Wednesday that all sides should continue to uphold the Iran nuclear agreement, and that the International Atomic Energy Agency (IAEA) has said many times Iran is in compliance with the deal.

Foreign Ministry spokeswoman Hua Chunying said the IAEA is the only international body with the right to supervise the agreement and make judgments about it, and China has noted that the agency has said several times Iran is in compliance.

Meanwhile, the Iranian Foreign Ministry on Tuesday dismissed recent allegations by Israeli Prime Minister Benjamin Netanyahu as lies aimed at influencing Trump's upcoming decision on the deal.

Foreign Ministry Spokesman Bahram Qasemi said in a statement that "the ridiculous propagandist presentations of the premier of the Zionist regime (of Israel) is one of the latest shameful and worthless shows about Iran's nuclear program".

In a televised presentation on Monday, Netanyahu disclosed files allegedly obtained by Israel's intelligence agency from Iran's "secret nuclear archive", saying the files prove Iran has secretly worked on nuclear weapons.

In another development, Morocco announced on Tuesday that it is severing ties with Iran, only a few years after normalizing their diplomatic relationship, over Iran's alleged backing of Western Sahara's separatist movement the Polisario Front, Xinhua reported.

Xinhua and Reuters contributed to this story.