Tehran Iran -- Iran's president said Wednesday that the Islamic Republic will stop exporting excess uranium and heavy water from its nuclear program as stipulated by the nuclear deal reached in 2015 with world powers. President Hassan Rouhani set a 60-day deadline for new terms to be reached by the nations still trying to keep the deal viable, and said if that didn't happen, Iran would resume enriching uranium to higher levels.

Rouhani's address to the nation came on the anniversary of President Trump's decision to unilaterally withdraw the U.S. from the landmark agreement. Rouhani said Iran wanted to negotiate new terms with the remaining partners in the deal, but acknowledged that the situation was dire.

Iran sent letters Wednesday on its decision to the leaders of Britain, China, the European Union, France and Germany via their ambassadors in Tehran. All were signatories to the nuclear deal and continue to support it. A letter also was given to Russia. Iranian Foreign Minister Mohammad Javad Zarif was to meet Wednesday in Moscow with his Russian counterpart.

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"We felt that the nuclear deal needs a surgery and the painkiller pills of the last year have been ineffective," Rouhani said. "This surgery is for saving the deal, not destroying it."

Starting today, Iran does not keep its enriched uranium and produced heavy water limited. The EU/E3+2 will face Iran's further actions if they can not fulfill their obligations within the next 60 days and secure Iran's interests. Win-Win conditions will be accepted. — Hassan Rouhani (@HassanRouhani) May 8, 2019

The 2015 agreement saw sanctions on Iran lifted in exchange for the regime putting limits on its nuclear program. After the U.S. withdrew from the accord, the Trump administration restored crippling sanctions against Iran, exacerbating a severe economic crisis. The Trump administration has vowed to reduce Iran's vital oil exports to zero, by pressuring other countries to stop buying Iranian petroleum products.

"If the five countries join negotiations and help Iran to reach its benefits in the field of oil and banking, Iran will return to its commitments according to the nuclear deal," Rouhani said.

However, Rouhani warned of a "strong reaction" if European leaders instead seek to impose more sanctions on Iran via the U.N. Security Council. He did not elaborate.

Zarif, on his visit to Moscow, issued his own warning via Twitter, saying that, "after a year of patience, Iran stops measures that (the) US has made impossible to continue." He said the remaining countries had "a narrowing window to reverse this."

On May 8 2018, US withdrew from #JCPOA, violated #UNSCR 2231 & pressured others—incl #E3—to do the same

After a year of patience, Iran stops measures that US has made impossible to continue

Our action is within the terms of JCPOA.

EU/E3+2 has a narrowing window to reverse this. — Javad Zarif (@JZarif) May 8, 2019

The Reuters news service cited sources in the office of French President Emmanuel Macron as saying worldwide sanctions could be reimposed on Tehran if it reneges on terms of the nuclear deal.

Iran moving missiles by boat, official says

There was no immediate response from the U.S. to Iran's partial withdrawal announcement, but it came three days after the White House dispatched an aircraft carrier and a bomber wing to the Persian Gulf over what it described as a new threat from Iran.

White House national security adviser John Bolton said Sunday evening that the decision to move the hardware, including four B-52 bombers, was in response to "a number of troubling and escalatory indications and warnings." He didn't provide details, but said the U.S. wanted to send a "clear and unmistakable" message to Iran that "unrelenting force" would meet any attack on U.S. interests or those of its allies.

"The United States is not seeking war with the Iranian regime, but we are fully prepared to respond to any attack, whether by proxy, the Islamic Revolutionary Guard Corps, or regular Iranian forces," he said.

A U.S. official said on Tuesday that the Trump administration's decision was based in part on intelligence indications that Iran had moved short-range ballistic missiles by boat off its shores. The movement, first reported by CNN, was among a range of recent indications that Iran might be considering or preparing to attack U.S. forces in the region, said the official, who spoke on condition of anonymity in order to discuss sensitive intelligence.

The official said it was not clear whether the boats with missiles represented a new military capability that could be used against U.S. forces or were only being moved to shore locations.

A Defense Department official told CBS News senior national defense correspondent David Martin earlier this week that the U.S. had detected "a number of preparations for possible attack" on U.S. forces at sea and on land.

"There is more than one avenue of attack or possible attack that we're tracking," the official said.

The nuke deal's terms

Western governments had long feared Iran's atomic program could allow it to build nuclear weapons. Iran has always maintained its program is for peaceful purposes.

Currently, the accord limits Iran to enriching uranium to 3.67 percent, which can fuel a commercial nuclear power plant. Weapons-grade uranium needs to be enriched to around 90 percent. However, once a country enriches uranium to around 20 percent, scientists say the time needed to reach 90 percent is halved. Iran has previously enriched to 20 percent.

Under the terms of the deal reached in 2015, Iran can keep a stockpile of no more than 300 kilograms (660 pounds) of low-enriched uranium. That's compared to the 22,046 pounds of higher-enriched uranium it once had.

The International Atomic Energy Agency -- the world's nuclear watchdog agency -- has repeatedly verified Iran's compliance with the nuclear deal since it was adopted, but President Trump, even before he was elected, disparaged the hard-won agreement as too generous to Iran.

His administration argued from the beginning that while Iran wasn't violating the stipulations of the deal, it was defying the "spirit" of the agreement, and the White House abandoned it for that reason -- much to the chagrin of the other parties involved.