"The main purpose of the United States in implementing the sanctions against Iran is to destroy the JCPOA," Deputy Foreign Minister Sayed Abbas Araqchi said, referring to the Joint Comprehensive Plan of Action, the deal engineered between Iran and the five permanent members of the UN Security Council, alongside Germany and the European Union.
He added that Tehran "will show a very clever reaction" to the imposition of sanctions.
Iranian Foreign Ministry spokesman Bahram Qasemi also warned that the "hostile" US measures would impact the implementation of the 2015 nuclear deal and said Tehran reserved the right to respond, according to state news agency IRNA.
"Iran with due patience and wisdom will take measure toward [its] national security and people's interests," he is quoted as saying.
President Donald Trump signed into law Wednesday morning legislation that levies new sanctions against Iran, alongside Russia and North Korea.
The bill seeks to ban anyone dealing with Iran's ballistic missile program from entering the US, and blocks transactions on properties held in the US by people associated with the program.
The Iran nuclear deal is designed to monitor and curtail Iran's nuclear program in exchange for economic sanctions relief. Some Iranian officials have suggested that the US posture is itself a violation of the nuclear pact.
Iran has yet to issue a formal response to the sanctions imposed by the US.
It's not clear what any retaliatory measures could be, since trade between the two nations is very limited and the US has no diplomatic presence in Iran. However, Iran could potentially use its influence in the region to thwart US foreign policy aims.
'Destructive, threatening' actions
On Wednesday, US Ambassador to the UN Nikki Haley condemned Iran's testing of a space launch vehicle
which could be converted into a ballistic missile, according to a UN press release.
"Our friends and allies in the United Kingdom, France, and Germany join us in calling out and condemning Iran's destructive and threatening actions," she said.
"The world must not allow Iran to act in defiance of the Security Council and its resolutions. The United States will be vigilant in ensuring that Iran is held accountable for such behavior."
She also accused Iran of aiding terrorist groups such as Hezbollah.
The country's ballistic missile program and alleged state sponsorship of terrorism are two items not covered by the nuclear deal.
Trump, on the campaign trail and since taking office, has frequently railed against the nuclear deal.
Trump has long promised he would take a tough line on Iran -- including his calls on the campaign trail for the US to tear up or renegotiate the agreement, which he has decried as "the worst deal ever."
However, he has since twice re-certified the deal, most recently in July
, extending the sanctions relief granted to Iran under the agreement. The US must certify to Congress every 90 days that Iran is complying with the deal.
At that time, the Trump administration coupled its certification to Congress of Iran's compliance with a blistering critique of Iran's non-nuclear activities, saying Iran was "unquestionably in default of the spirit" of the deal.
"The secretary of state -- and the President -- intends to emphasize that Iran remains one of the most dangerous threats to the US and to regional security," a senior administration official said after the deal was re-certified.
"Moving forward, the administration intends to employ a strategy that will address the totality of Iran's malign behavior and not just focus on the nuclear deal," the official said at the time, foreshadowing the sanctions bill.
Leader endorsed for second term
Deputy Foreign Minister Araqchi's response came as Iranian President Hassan Rouhani was endorsed by Iranian Supreme Leader Ayatollah Ali Khamenei for his second term after being re-elected in a landslide in May.
Speaking at the endorsement ceremony, Khamenei told the senior officials present to stand up against "any hegemonic power" and labeled the United States "the most aggressive" of all.
"Decades of international relations show us that the price of surrendering to such powers is much heavier than the expense that we pay for being independent of them," he said.
In attendance, according to Iran's state-run Islamic Republic News Agency
, was North Korea's second-most powerful leader, Kim Yong-nam. The news agency said senior officials from 92 countries are in Tehran for an oath-taking ceremony Saturday.
Rouhani brokered the deal with then-US President Barack Obama in 2015, alongside other world leaders and multinational groups.
In Tehran, Arash Asgiari, a 28-year-old hospitality worker, told CNN that sanctions relief after the nuclear deal two years ago improved his livelihood, in part because more foreigners have access to his business.
"My life has improved financially. I am paid better. I see many foreigners coming to Iran. My business is more prosperous," Asgiari said Thursday.
But said he doesn't trust the United States, citing its wars in Iraq and Afghanistan.
"I don't believe the US wants to improve things here," he said. "Look at Iraq. ... Look at Afghanistan -- they destroyed it."