The war games, the duration of which was not specified, aim to prepare the Guards for "potential security and military threats" in the strait, state TV said, after the United States deployed a large naval force to the area.

Iranian hardline politicians have repeatedly threatened to block the strait, especially during times of heightened tensions with the United States, but it has never been closed.

The strategic waterway sees about 20 percent of the world's oil production pass through it.

The exercises, overseen by Guards chief General Mohammad Pakpour, aim to bolster the IRGC's ability to react quickly, Iranian media reported. The Guards are the ideological arm of Iran's military.

The drills take place as Tehran and Washington ready for a new round of talks in Geneva on Tuesday, mediated by Oman. It also comes at a time of heavy US military deployment in the Gulf.

The decades-long enemies resumed nuclear negotiations on February 6 in Oman, their first since diplomacy broke down last June during the Iran-Israel war, which saw Israel and the United States strike Iranian nuclear facilities.

US President Donald Trump has been pressuring Iran to reach an agreement, especially with recent US naval force deployments to the region that he has described as an "armada".

After sending the aircraft carrier USS Abraham Lincoln and escort battleships to the Gulf in January, Trump said on Friday that a second aircraft carrier, the Gerald R. Ford, would depart "very soon" for the Middle East.

On Monday, IRGC navy official Mohammad Akbarzadeh warned that all foreign ships in the region were "under full intelligence surveillance and within the reach of our defence power".

"The armed forces are fully prepared, monitoring the enemy's movements and never ignoring threats," he was quoted by the state-run IRNA news agency as saying.