WASHINGTON — The Biden administration blocked entry on Tuesday to a number of dozen web sites linked to Iran, American and Iranian officers mentioned, simply as negotiations to deliver america and Tehran again into a world nuclear accord seemed to be nearing a last determination.

The US blocked the websites days after Iran held a presidential vote to put in Ebrahim Raisi, the nation’s former chief choose and shut ally of the clerical authorities’s supreme chief, as its prime elected official. The US has accused Mr. Raisi of human rights abuses, and has imposed sanctions that each one however forestall official dealings with him.

Among the many web sites that have been seized was Iran’s state-owned Press TV, which on Tuesday afternoon displayed a red and white banner, in English and Persian, warning that it was the topic of felony and intelligence investigations. The seals of the F.B.I. and the Commerce Division have been additionally prominently pictured.

Additionally seized have been web sites for Iran-backed Houthi militia in Yemen and satellite tv for pc and TV information channels which might be devoted to reviews from the holy Shiite metropolis of Karbala, Iraq, based on the Iranian information media.

One U.S. nationwide safety official mentioned the web sites, about three dozen in all, have been linked to disinformation efforts by Iran and different teams backed by Tehran. A number of concerned terrorist organizations that focused coalition forces stationed abroad, mentioned the official, who spoke on the situation of anonymity to explain the operation earlier than it was introduced.

The spokesman for Iran’s mission to the United Nations, Shahrokh Nazemi, mentioned america was attempting to muzzle free speech.

“Whereas rejecting this unlawful and bullying motion, which is an try at limiting the liberty of expression, the problem will probably be pursued by authorized channels,” Mr. Nazemi mentioned.

The semiofficial Fars Information Company, which is affiliated with Iran’s Islamic Revolutionary Guards Corps, accused the American authorities on Tuesday of focusing on web sites that belonged to the so-called axis of resistance — how Tehran and its allies describe proxy militia teams in Yemen, Iraq, Lebanon and Syria that obtain coaching and funding from Iran.

American officers additionally seized Fars’s web site in 2018, when it was registered as a .com area. The information company switched to an Iranian area of .ir and was again on-line quickly afterward — a technique that Press TV mentioned on Tuesday that it will observe.

Amir Rashidi, the director of digital rights and safety at Miaan Group and an skilled on Iranian know-how, likened the safety motion to “a recreation of whack-a-mole — you shut this area, they open one other and there may be nothing they’ll do.”

“The way in which to fight disinformation is data and strengthening unbiased journalism, giving the inhabitants web entry,” Mr. Rashidi mentioned.

It was unclear how the safety operation would possibly have an effect on the nuclear negotiations, which have been underway in Vienna since April.

Diplomats from the world powers which might be attempting to revive the accord mentioned after conferences in Vienna on Sunday that the talks have been making some progress, with the highest Russian negotiator, Mikhail Ulyanov, even predicting a possible breakthrough by mid-July. The negotiators have been to return to their capitals this week to transient their governments on the newest developments.

American and Iranian officers aren’t negotiating straight, leaving it to diplomats from Europe, China and Russia to function intermediaries within the talks, that are aimed toward bringing america and Iran again into compliance with the 2015 nuclear accord that america left three years later on the orders of President Donald J. Trump.

President Biden has mentioned that rejoining the nuclear settlement is one in all his prime overseas coverage priorities, though his aides have largely downplayed any certainty {that a} deal will probably be struck.

After the Trump administration withdrew from the accord, it issued a raft of highly effective monetary sanctions which have deeply bruised Iran’s financial system, in an try to power Tehran to barter a brand new deal that may additionally curb its ballistic missile applications and proxy militias throughout the Center East.

As a substitute, Iran has steadily elevated its manufacturing of enriched uranium, the gas that’s essential to make a nuclear weapon, far past the boundaries set by the 2015 accord. That has alarmed world powers and worldwide inspectors who urgently wish to deliver Iran again into compliance — requiring america to carry no less than a few of its sanctions.

The negotiations largely have been hung up on which American sanctions will probably be eliminated. The Biden administration additionally has vowed that the deal will function a platform for brand new talks targeted on Iran’s missiles and militias applications — a proposal that Mr. Raisi has already rejected.

Some officers imagine that Iran’s supreme chief, Ayatollah Ali Khamenei, will conform to the nuclear deal earlier than Mr. Raisi is inaugurated in early August. That will shield Mr. Raisi from any home backlash for coping with america — particularly if the sanctions aid doesn’t instantly bolster Iran’s financial system.