Iran claims to have missiles that can travel 2,000 kilometres, placing much of the Middle East, including Israel, within range.
Iran's paramilitary Revolutionary Guard has inaugurated a new underground facility designated for missile storage, the country's state TV reported.
The report quotes Guard commander General Hossein Salami as saying that cruise and ballistic missiles will empower the force's navy even more.
The TV report on Monday showed footage of scores of missiles in an enclosed space resembling an underground corridor. It did not say where the facility is located nor how many missiles are stored there.
Since 2011, Iran has boasted of underground facilities across the country as well as along the southern coast near the strategic Strait of Hormuz.
The US and its Western allies see Iran’s missile program as a threat, along with the country’s nuclear programme, particularly after Tehran gradually breached its commitments to the 2015 nuclear deal with world powers, following the Trump administration's withdrawal from the deal in 2018.
Last July, the Guard launched underground ballistic missiles as part of an exercise involving a mock-up American aircraft carrier in the Strait of Hormuz, highlighting its network of subterranean missile sites.
Since Iran's bloody 1980s war with Iraq, which saw both nations fire missiles on cities, Iran has developed its ballistic missile program as a deterrent, especially as a UN arms embargo prevents it from buying high-tech weapons systems.
The underground tunnels help protect those weapons, including liquid-fuelled missiles that can only be fuelled for short periods of time.
US nuclear stance
The United States should act quickly to revive Iran's nuclear deal, because once Iran's presidential election period kicks off it is unlikely much will happen until later this year, Iranian Foreign Minister Javad Zarif said on Monday.
Speaking at the European Policy Centre think tank, Zarif repeated Tehran's longstanding demand that Washington return first to compliance by lifting sanctions.
President Joe Biden aims to restore the deal, but Tehran and Washington each want the other side to comply first.
"The Europeans are used to compromise. Iran and the United States are not. The Americans are used to imposing, and we are used to resisting," Zarif said. "So now is the time to decide will we both compromise and go back to the JCPOA, or will we go back to our own paths?"
Zarif said that he had seen no change between the Biden administration and the Trump administration's policy of maximum pressure to force Iran back to the negotiating table.