US mulls more sanctions as Iran unveils ballistic-missile facility
"We will use everything within our power to put additional sanctions on Iran, Syria and North Korea to protect American lives," Mnuchin told the House Ways and Means Committee on the administration's budget proposal, adding that his department is reviewing the licenses required by US aviation giants Boeing and Airbus to sell airplanes to Iran.
Iran has been desperate to renew its ageing fleet of planes, but was largely blocked from dealing with major aircraft manufacturers until a 2015 accord with world powers that eased global sanctions in exchange for curbs to its nuclear programme.
The US has maintained its own sanctions, which block almost all trade with Iran, but plane manufacturers were given a specific exemption under the nuclear deal.
Last month, Iran agreed to buy Boeing jets worth $3 billion in a second major deal since sanctions were eased last year.
In September, Washington approved the sale of 80 Boeing and 100 Airbus planes to Iran Air. The first few Airbus jets have already arrived in Tehran.
Many US lawmakers have opposed the sales, saying that Iranian airlines have been used to ship weapons and troops to Syria and other conflict zones.
Iran - a key backer of Syrian President Bashar al-Assad - has been seen as one of the biggest obstacle to settling the conflict in Syria.
Companies across the world are waiting to see whether US President Donald Trump makes good on his campaign threat to tear up the nuclear deal.
The first test will come in June when he will decide on whether to renew the sanctions waivers that keep the deal in effect.
Iran 'will continue to develop' its missile programme
On Thursday, Fars news reported that Iran has built a third underground ballistic missile production factory.
The semi-official news agency quoted the head of the Republican Guard's airspace division Amirali Hajizadeh saying Tehran will continue developing its missile programme.
"Iran's third underground factory has been built by the Guards in recent years ... We will continue to further develop our missile capabilities forcefully," Hajizadeh said.
The development is likely to fuel further tensions in the region between Iran and its Arab neighbours, and with the United States and Israel.
"It is natural that our enemies America and the Zionist regime (Israel) are angry with our missile program because they want Iran to be in a weak position," Hajizadeh said.