Iran's Foreign Minister Mohammad Javad Zarif has said Tehran had not violated its 2015 nuclear deal with world powers after its stockpiles of enriched uranium breached a limit set in the landmark accord.

Iran on Monday announced its reserves of enriched uranium had surpassed the 300kg cap and said its next step would be to enrich uranium above the 3.67 percent limit in the accord, unless European powers did more to protect the Iranian economy from harsh US sanctions.

Last year, the United States unilaterally withdrew from the deal, which imposed limits on Iran's nuclear activity in return for removing international sanctions on its economy. After leaving the accord, the US reimposed sanctions on Tehran.

Making light of the US reaction on Tuesday, Zarif tweeted a screengrab of the statement, asking: "Seriously?"

The foreign minister, who has been personally targeted in the latest round of US sanctions, said the Iranian move did not violate the accord, whose remaining signatories include China, Russia, Germany, France and the United Kingdom.

"We had previously announced this and were transparent in saying what we are going to do," he told reporters. "We consider it our right, reserved in the nuclear deal."

"Actions by the Europeans have not been enough, so we will move ahead with our plan," he said.

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