Iranian Foreign Minister Mohammad Javad Zarif said on Sunday that Iran would adhere to the 2015 nuclear deal so long as European signatories also remain committed to the agreement.

"The resistance of the Europeans (against the US) will show whether the nuclear agreement can be carried forward or not," Zarif said.

US President Donald Trump said on Friday he would not "re-certify" the deal that dropped sanctions against Iran in exchange for Tehran halting its nuclear program. US Congress now has 60 days to decide whether to reapply US sanctions against the country.

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Zarif was optimistic that European leaders would continue to support the deal given their geopolitical and economic interests in Iran. He also said an abiding commitment would also show whether Europe "could play its own role independent of the US in the world."

Zarif's comments echo those of Iranian President Hassan Rouhani who earlier said Iran  would not withdraw  from the agreement if the remaining signatories — the four UN Security Council members Russia, China, France and Britain plus non-council member Germany – also remained committed.

Read more: What is the Iran nuclear deal?

Britain and Germany pledge support

British Prime Minister Theresa May and German Chancellor Angela Merkel on Sunday said their governments would not withdraw from the nuclear deal.

During a call, "they agreed the UK and Germany both remained firmly committed to the deal," a British government spokeswoman said.

"They also agreed the international community needed to continue to come together to push back against Iran's destabilizing regional activity, and to explore ways of addressing concerns about Iran's ballistic missile program," the spokeswoman added.

New Iranian threats

On Saturday, Zarif said Trump's speech had violated the terms of the nuclear agreement.

According to the Iranian minister, the US had not implemented the deal "in good faith" and had not "refrained from reintroducing or reimposing" sanctions against Iran's nuclear program.

"I have already written nine letters [to EU foreign policy chief Federica Mogherini] listing the cases where the United States has failed to act on or delayed its commitments under the JCPOA," Zarif said, referring to the name of the nuclear agreement by its official acronym.

Mogherini had negotiated the deal along with representatives from the US, Britain, France, China, Russia and Germany.

Zarif warned that Tehran would respond to any new US sanctions with a "reciprocal measure."

Read more: Iran nuclear deal: What's next?

If deal collapses, renewed enrichment?

The head of Iran's Atomic Energy Organization (IAEA), Ali Akbar Salehi, on Saturday warned that Tehran would stop allowing unannounced UN nuclear inspections if the agreement fell apart.

He said Iran's adherence to the Additional Protocol of the Non-Proliferation Treaty, which allows the IAEA inspections, would be "meaningless" without the wider agreement.

He also warned that Iran would restart production of highly enriched uranium at 20 percent if the US reintroduced sanctions, which he said the country could do "within four days."

Nuclear weapons require 90 percent enriched uranium, but 20 percent enriched uranium can be converted into 90 percent in a short period of time.

amp/sms (Reuters, dpa, AFP)