Rafael Grossi said the three-month bridge agreement between the U.N. agency and Iran was "quite fragile."
Biden approved airstrikes on Iranian-backed Iraqi militia fighters in Syria in retaliation for a rocket attack on American troops in Iraqi Kurdistan.
Text inside the graphic posted by the Iranian news agency indicates that "revenge is inevitable" against former President Donald Trump for ordering the killing of Iranian general Qassem Soleimani.
Tensions are high as Trump's final weeks in office coincide with the Soleimani anniversary and fresh violence in Iraq.
In all cases, it would be better to capture war criminals alive, but if that is not possible, it is entirely lawful and moral to neutralize them and the threats they pose, while limiting the collateral damage to others.
The recent assassination of top nuclear scientist Mohsen Fakhrizdeh threatens to plunge U.S.-Iranian ties into deeper chaos before President-Elect Joe Biden can attempt to thaw relations.
The CEO of a technology firm has claimed that Iranian forces used a Russian-made radar system to identify and track American warplanes in January.
"We have made great progress in the field of strategic and deterrent weaponry," Iranian President Hassan Rouhani said.
Supreme Leader Ayatollah Ali Khamenei made the threat during a meeting with new Iraqi Prime Minister Mustafa al-Kadhimi, urging Baghdad to expel U.S. troops from the country.
Agnes Callamard, the U.N. special rapporteur on extrajudicial, summary or arbitrary executions, said the U.S. had failed to provide evidence to support the need for the January drone strike.
Scott Modell, adjunct professor at Georgetown University, debates The American Conservative's Curt Mills.
Tehran prosecutor Ali Alqasimehr said Trump and 35 others are now facing "murder and terrorism charges" which Iran will pursue even if the president loses the November election.
The report outlining the administration's legal justifications for killing the Iranian general does not cite an "imminent attack," which Trump and some of his top officials claimed was the reason.
The threat was made in Iran's parliament by the lawmaker who represents the area that former Quds Force commander Qassem Soleimani came from.
Ayatollah Ali Khamenei told worshippers in Tehran on Friday that the strike against American targets in Iraq should be considered a "day of Allah."
Benjamin B. Ferencz, 99, said he "cannot stay silent" on what he termed the "murder" of the influential Iranian commander.
Douglas London, a 34-year veteran of the CIA, warned that Trump is primarily focused on "celebrity" and "headlines."
Moderates from across the political spectrum showed the biggest decline in consumer confidence.
Iran has used the killing to rally support at home and abroad, but now has to walk the tightrope between underwhelming its allies and provoking an all-out war.
James L. Jones said the president should not listen to the "appeasers" who want to return to "normal business."
"In pursuing the case of the downed plane, justice will be implemented irrespective of any circumstances," Iran's judiciary chief said.
"[Trump] would kind of mix up both the impeachment issue as well as the attack on Soleimani," Representative Raja Krishnamoorthi said.
"It is unconscionable that an American president would mock Islam and Muslims in such a derogatory manner," a spokesperson for the Council on American-Islamic Relations told Newsweek.
Soleimani was considered Iran's top military commander until he was assassinated in a U.S. drone strike in Baghdad earlier this month.
There is no need for the Trump administration to degrade diplomatic dialogue or hide the legitimate motivations for conflict with Iran under the guise of fighting terrorism.
Instead of overreact to every Iranian action, the U.S. needs to keep the scale of the Iranian threat in perspective—and make a pragmatic offer to Tehran.
"The present wave of protests has the potential of developing into a revolution," Hilal Khashan, a professor at the American University of Beirut, told Newsweek.
Esper appeared to contradict the president on Sunday, when he said he had not seen evidence that Iran was planning attacks on four American embassies.