In a call with Hassan Rouhani, Macron expressed his concern over weakening the nuclear agreement.

Iran has surpassed the cap on uranium enrichment set by a 2015 nuclear deal with world powers, a spokesman for Iran's Atomic Energy Organization said Monday, warning that Tehran would take further steps to reduce its commitments under the accord.

Behrouz Kamalvandi, speaking to local news agencies, said Iran has exceeded the 3.67% limit and is now enriching uranium at 4.5%, a rate far below the 90% needed to produce a nuclear weapon.

The move was designed to pressure Europe to reset the terms of the nuclear agreement following a U.S. withdrawal from the pact last year. The deal curbed Iran's atomic energy activities in exchange for widespread sanctions relief.

Iran says European nations have failed to compensate Tehran for economic losses now that the United States has reimposed trade and other restrictions lifted under the deal.

The International Atomic Energy Agency announced Monday that its inspectors have verified that Iran is enriching uranium above 3.67% uranium-235. IAEA spokesman Fredrik Dahl said in an email that the agency's director general, Yukiya Amano, has informed the IAEA Board of Governors of that development. The IAEA, a United Nations nuclear watchdog, monitors Iran's nuclear activities.

Before the 2015 nuclear agreement was signed, Iran at one point had more than 22,000 pounds of enriched uranium, a portion of it enriched to nearly 20%. Under the accord, Iran agreed to get rid of the vast bulk of its enriched-uranium stockpile.

Iran has said that it will scale back its obligations under the accord at 60-day intervals and gave Europe another deadline of Sept. 5 before taking a third step to breach the agreement.

Iran's Foreign Ministry spokesman, Abbas Mousavi, said Monday that if European nations "do not fulfill their commitments seriously and do not do anything more than talk, Iran's third step will be harder, more steadfast and somehow stunning," the Associated Press reported.

Kamalvandi suggested Monday that his agency could raise Iran's enrichment level to 20% or reinstall advanced centrifuges deactivated under the deal.

"For now, we don't need 20%" enrichment, he said in an interview aired by Iran's state broadcaster, adding that the 4.5% rate was sufficient to supply fuel to Iran's power plants.

"But if we do, since we have already exceeded 3.67%, we have no limitations or obstacles to do so," he said.

Iran has said it needs uranium enriched to about 20% of U-235, a fissile isotope, for use in a 52-year-old, U.S.-supplied research reactor in Tehran to produce isotopes for medical and scientific purposes. The 2015 nuclear deal required Iran to fabricate an existing stockpile of 5% to 20% enriched uranium into fuel plates for the research reactor, transfer the material out of Iran in a commercial deal or dilute it to 3.67 percent or less - a level suitable for use as reactor fuel in Iran's Bushehr nuclear power plant. Any additional fuel needed for the research reactor would be purchased by Iran at international market prices, according to the pact.

Mousavi said Iran has "no hope" that the deal's remaining signatories would salvage the agreement.

"But the door of diplomacy is open," he said. Vice President Mike Pence told a pro-Israel Christian group Monday that the Trump administration will sustain its maximum-pressure campaign against Iran, according to The Associated Press. Speaking in Washington, he said the U.S. "will never allow Iran to obtain a nuclear weapon." He added: "Iran must choose between caring for its people and continuing to fund its proxies, who spread violence and terrorism throughout the region and breathe out murderous hatred against Israel."

In a phone call with Iran's President Hassan Rouhani on Saturday, French President Emmanuel Macron expressed his "deep concern over the danger of further weakening" the nuclear agreement and "the consequences that would necessarily ensue."

The two leaders "agreed to explore, between now and July 15, the conditions for a resumption of dialogue involving all the parties," the French government said in a statement.

Wendy Sherman, a former State Department official who was the lead U.S. negotiator in the talks with Iran, said that Iran's steps so far are reversible but that each step "does move us down a more dangerous path."

"This could spiral out of control quite quickly, depending on U.S. actions," she said.

Robert Malley, an adviser in the Obama White House who also participated in the negotiations, said Iran's actions so far are not a threat, yet.

"For the time being, it's more political signaling than proliferation," he said. "But it will continue to get worse. Iran will move away from the (2015 nuclear deal) if things do not change. It is telling the United States, if it wants to engage in brinkmanship, two can play that game."