The United States has hit Tehran with new sanctions, targeting 31 Iranian scientists, technicians, and companies it says have been involved in the country's nuclear and missile research and development programs.
In a statement on March 22, the U.S. State Department said the 14 individuals and 17 entities targeted were affiliated with Iran's Organization for Defense Innovation and Research.
It said the group, known by its Persian acronym SPND, was "established by Mohsen Fakhrizadeh, the head of the regime's past nuclear weapons program."
President Donald Trump's administration "continues to hold the Iranian regime accountable for activities that threaten the region's stability and harm the Iranian people. This includes ensuring that Iran never develops a nuclear weapon," the statement said.
The U.S. Treasury Department said that among those targeted was the Shahid Karimi group, which it said works on missile and explosive-related projects for the SPND, and four associated individuals.
The government "is taking decisive action against actors at all levels in connection with [the SPND] who have supported the Iranian regime's defense sector," Treasury Secretary Steven Mnuchin said in a statement.
"Anyone considering dealing with the Iranian defense industry in general, and SPND in particular, risks professional, personal, and financial isolation," he said.
The Treasury Department said the sanctions -- which freeze any U.S. assets of those named and bans U.S. dealings with them -- target current SPND subordinate groups, supporters, front companies, and associated officials.
The announcement of new sanctions came as Secretary of State Mike Pompeo was in Beirut warning Lebanese officials to curb the influence of the Iran-backed Hizballah movement.
Pompeo said that Hizballah is a terrorist organization and should not be allowed to set policies or wield power despite its presence in Lebanon's parliament and government.
On March 21, Iranian Supreme Leader Ayatollah Ali Khamenei said that Tehran intended to boost its defense capabilities despite pressure from the United States and its allies to restrict the country's ballistic-missile program.
The United States has urged the UN Security Council to impose sanctions on Iran over its recent ballistic-missile test and the launches of two satellites, saying they violated Security Council resolutions.
On March 7, acting U.S. Ambassador to the UN Jonathan Cohen condemned what he called "Iran's destabilizing activities" in a letter to UN Secretary-General Antonio Guterres.
Cohen called on Tehran "to cease immediately all activities related to ballistic missiles designed to be capable of delivering nuclear weapons."
The U.S. envoy's statement cited a 2015 UN resolution that "called upon" Iran to refrain for up to eight years from tests of ballistic missiles designed to deliver nuclear weapons.
The United States has reimposed sanctions on Iran after withdrawing from a landmark 2015 agreement under which Tehran agreed to restrictions on its nuclear program in exchange for sanctions relief.
Trump said that Tehran was not living up to the "spirit" of the accord because of its support of militants in the region and for continuing to test nuclear weapons and ballistic missiles.
Tehran has denied it supports terrorist activity and says its missile and nuclear programs are strictly for civilian purposes.