The surest way

European countries have said they remain committed to the agreement, seeing it as the surest way to safeguard their national security.

"The problem is: What next?" one of the European diplomats said, referring to concerns that the US is eyeing government change as the sanctions' end goal. Both diplomats spoke on condition of anonymity, as they were not authorized to brief the media on ongoing negotiations.

If the reimposed sanctions caused the government in Teheran to collapse, Iran would likely devolve into civil war like what unfolded in Syria, the diplomat said.

A deepening of Iran's economic crisis could also lead to an influx of refugees and migrants into Europe like that seen on the heels of the Syrian conflict.

Supporters of the Iran agreement have long argued that the US departure would alienate European allies who partnered with the US in the negotiations.

We "remain firmly committed to ensuring (the deal) is upheld and we continue to abide by our commitments," the second European diplomat said. "If we cannot fulfill these, this risks Iran deciding that it no longer has to abide by the restrictions."

Iran's economy was plunged into a downward spiral following Trump's announcement that the US was scrapping the deal.

AP-XINHUA-REUTERS