Javad Zarif was appointed foreign minister by President Hassan Rouhani in 2013.

The Trump administration imposed sanctions on Iranian Foreign Minister Mohammad Javad Zarif on Wednesday in a dramatic step bound to further escalate tensions with Tehran.

A senior administration official said Zarif had acted more as a "propaganda minister" than a diplomat, and Secretary of State Mike Pompeo said Zarif was "complicit" in Iran's support of terrorists, torture and other malign activity around the world.

Zarif mocked the designation in a tweet tinged with sarcasm.

"The US' reason for designating me is that I am Iran's 'primary spokesperson around the world,' " he tweeted. "Is the truth really that painful? It has no effect on me or my family, as I have no property or interests outside of Iran. Thank you for considering me such a huge threat to your agenda."

A Treasury Department statement said Zarif was sanctioned because he "acted or purported to act for or on behalf of, directly or indirectly" Iran's supreme leader, Ali Khamenei, who was sanctioned in late June. At that time, Treasury Secretary Steven Mnuchin said measures would also be taken against Zarif, but they were delayed after State Department officials argued that they would close the door to diplomacy.

Trump has frequently expressed a desire to talk with Iranian leaders, even as his administration deepens a maximum pressure campaign that has devastated the Iranian economy.

An administration official said Trump remains ready to speak with Iranian leaders - just not Zarif.

"If we do have an official contact with Iran, we would want to have contact with someone who is a significant decision-maker," a senior administration official said when asked whether sanctioning Iran's chief diplomat would limit U.S. ability to negotiate with Iran, if negotiations ever take place.

Zarif "would not be the president's selected point of contact," said the official, who like others spoke on the condition of anonymity under rules set by the administration.

While Trump has continued to say he is open to negotiations without preconditions, both Pompeo and national security adviser John Bolton have indicated that the list of conditions is long. Pompeo, in a statement issued Wednesday by the State Department, said that the administration "continues to seek a diplomatic solution," but that "the only path forward is a comprehensive deal that addresses the full range of [Iranian] threats."

"Until then," it said, "our campaign of diplomatic isolation and maximum economic pressure will continue."

Sen. Rand Paul, R-Ky., a Trump confidant who met with Zarif recently to discuss back-channel communications, tweeted his concern: "If you sanction diplomats you'll have less diplomacy."

When Zarif visited New York this month on official U.N. business, Pompeo complained about the interviews he granted to American journalists. Pompeo said that out of fairness, he should be allowed to address Iranian citizens directly on state television.

Mnuchin tried to highlight the dichotomy of Zarif's ability to harness free speech platforms to spread his views while denying it to ordinary Iranians.

"At the same time, the Iranian regime denies Iranian citizens access to social media, Foreign Minister Javad Zarif spreads the regime's propaganda and disinformation around the world through these mediums," he said.

The sanctions freeze all U.S. assets and prohibit any U.S. person or entity from dealings with Zarif, and they threaten sanctions against those in other countries that deal with him.

The sanctions also prohibit travel to the United States, which is already banned for Iranian officials. Under international agreement, the United States must admit those traveling to the United Nations in their official capacity. Zarif visited the United Nations in July, although the State Department limited him to U.N. headquarters and the Iranian diplomatic mission in New York.

Zarif, who speaks fluent English and has a ready smile and generally calm demeanor, "has the veneer, the masquerade if you will, of being the sincere and reasonable interlocutor for the regime," the administration official said. "Our point today is he is no such thing."

While serving as the "international face of this regime," the official said, Zarif has been "heading propaganda and disinformation campaigns" while "defending the regime's persecution of the Iranian people . . . as well as suppression of free speech," and support for the imprisonment of Washington Post correspondent Jason Rezaian for 18 months, from 2014 to 2016.

Tensions between Washington and Iran have been growing since the Trump administration withdrew from the 2015 international nuclear deal last year and began its "maximum pressure" campaign. Initially, Tehran appeared to be exercising a policy of "maximum patience," hoping it could outlast Trump's time in office. But Iran became more aggressive as the United States tightened sanctions that have devastated the economy. It has been gradually breaching the nuclear agreement, shot down a U.S. drone in the Strait of Hormuz and challenged oil tankers traversing the waterway.

The sanctions announcement came on the eve of a Thursday U.S. deadline to renew or let lapse waivers that allow Europe, China and Russia to continue nuclear nonproliferation projects with Iran under the nuclear deal. After the U.S. withdrawal, Trump reimposed sanctions on Iranian oil exports and this year declined to renew waivers that exempted several Iranian customers from that ban.

Behnam Ben Taleblu, an Iran expert with the Foundation for Defense of Democracies, said the move against Zarif will undercut Iran's efforts to get out from under the sanctions.

"Zarif's recent strategy, as exemplified by tweets since April and his two trips to NYC, has been to try to lure President Trump into premature diplomacy and watering down sanctions. But this high-level designation shows that trying to cleave apart the administration is not going to be an easy task," he said.

Zarif was appointed foreign minister by President Hassan Rouhani in 2013, and he led negotiations that preceded the 2015 nuclear deal. In February, he resigned from his post. Although he gave no reason, media reports said he was angered at not being informed of a visit to Tehran by Syrian President Bashar Assad. Rouhani rejected his resignation, and he continued in his post.

From 2002 to 2007, Zarif served as Iran's permanent representative to the United Nations, as well as in other senior diplomatic posts. Zarif, 60, first left Iran as a teenager to attend a college preparatory school in San Francisco. He earned bachelor's and master's degrees in international relations from San Francisco State University, and a second master's and a doctorate in international law and policy from the University of Denver.