Iran's top nuclear negotiator, Abbas Araghchi, talks to journalists after meeting senior officials from the United States, Russia, China, Britain, Germany and France in Vienna in October 2015. (Heinz-Peter Bader/Reuters)

New U.S. sanctions targeting Iran are a breach of its nuclear deal with world powers and an attempt to abolish the accord, Iranian officials said Thursday, adding that the government will respond to what it sees as an escalation of U.S. aggression.

“We believe that the nuclear deal has been violated, and we will react appropriately,” Deputy Foreign Minister Abbas Araghchi said on state television Thursday.

The deal curbed Iran’s nuclear activities in exchange for the removal of some sanctions, while the new measures target anyone involved in Iran’s ballistic missile program and its powerful Revolutionary Guard Corps.

The “belief in Washington is that . . . Iran must be put under pressure,” Araghchi said. And the goal of the new sanctions, signed by President Trump on Wednesday, is “to destroy” the 2015 agreement so that Iran will withdraw.

The administration has criticized the deal for its narrow focus on the nuclear program, without addressing issues such as Iran’s support for proxy militias and its growing ballistic missile arsenal. Trump has questioned the “utility of the agreement,” Secretary of State Rex Tillerson said in remarks at the State Department on Tuesday.

The “agreement dealt with a very small slice of Iran’s threats,” Tillerson said. “It was kind of like we put blinders on and just ignored all those other things.”

But even as the United States ramps up pressure on Iran — including threats to leave the pact — officials in Tehran have moved cautiously in response, weighing the cost of potential conflict with the benefits of remaining part of the deal.

Before the agreement, which ended the country’s isolation, Iran probably would have balked at calls for diplomacy. As a regional power, it has defied the international community, building up missile defense and backing proxy forces across the region.

[Power struggle escalates between Iran’s president and hard-liners]

But under the nuclear deal, Iran has rejoined the global economy and is now keen to avoid blame for the collapse of the agreement. Trump recently certified Iran’s compliance with the deal, an authorization he is required to make to Congress every 90 days, but has suggested he may not do so again in the fall, without saying why.

“President Trump made clear that, in terms of the fate of the nuclear deal, the administration’s latest certification of Iranian compliance was only a temporary reprieve — a stay of execution,” said Robert Malley, who served as the White House coordinator for the Middle East under President Barack Obama.

So far, Iran “has appeared content to sit back and allow the [Trump] administration to further isolate itself” on the nuclear deal, said Malley, who is now vice president of policy for the Brussels-based International Crisis Group. “But that calculus could change.”

Iran, experts say, could continue to adhere to the agreement and seek assurances from Europe and Russia that they would refuse any U.S. attempt to renegotiate. The European Union has countered Trump’s calls to ditch the accord, reminding the administration that it belongs to the international community.

If the White House decided to declare Iran noncompliant, it would probably be based “on little to no valid evidence,” said Richard Nephew, former coordinator for sanctions policy at the State Department.

But Iran could still push the technical limits of the deal with “small incremental steps that restart its nuclear program,” he said.

It could also restart all of its nuclear activity, which it says is for peaceful purposes, or use its military assets or proxy forces to strike U.S. interests in the region.

Iran and the United States have skirmished in the waters of the Persian Gulf, where the U.S. Navy stations its 5th Fleet. American forces and militias loyal to Iran also fight in proximity in Iraq and Syria, where they are both battling the Islamic State.

“Having Iranian proxies take aim at the U.S. presence in Iraq or Syria could trigger powerful U.S. retaliation, which quickly could snowball,” Malley said.

[The United States and Europe are on a collision course over Iran]

According to Ali Vaez, senior Iran analyst at the International Crisis Group, rising tensions “could push Iran to double down on means of deterrence it considers essential to its national security,” including missile defense and support for regional proxies.

Last week, Iran successfully fired its satellite-carrying Simorgh launch vehicle into space, prompting the U.S. Treasury Department to come back with more sanctions.

Iran’s parliament, reacting to the sanctions bill as it made its way through Congress, recently fast-tracked funding for the country’s ballistic missile program and Revolutionary Guard Corps.

According to Abbas Aslani, world news editor at Iran’s privately run Tasnim news agency, Iran “will not violate” the nuclear agreement but neither will it “abandon or compromise on its defense capabilities, including the missile program.”

Iran’s hard-liners, many of whom opposed the deal as one that granted too many concessions, may use the tensions to press for some sort of retaliation. The deal was negotiated under Iranian President Hassan Rouhani, a moderate recently elected to a second term.

He fired back at domestic critics Thursday at a ceremony marking his formal endorsement by Iran’s supreme leader, Ayatollah Ali Khamenei, who has the final word on all matters of the state.

Iran survived some of the toughest sanctions “through a combination of the power of diplomacy and deterrent defensive power,” the Associated Press quoted Rouhani as saying. During his second term, Iran will “insist on constructive engagement more than before.”

But it is unclear how long Rouhani will maintain his pro-diplomacy rhetoric, which has already “become increasingly more critical of the Trump administration,” said Farzan Sabet, a fellow at Stanford University’s Center for International Security and Cooperation.

Still, conflict between the United States and Iran is “not preordained,” Malley said, and both sides could back down.

“But that means that the survival of the nuclear deal and avoidance of military conflict depend on the Trump administration showing restraint and the Iranian regime displaying wisdom,” he said. “Given what we know of the two, what are the odds of that?”

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