Iran has begun five days of large-scale war games to simulate attacks on its nuclear sites, officials said, warning it will retaliate if provoked.
The head of Iran's air defence said the aim of the exercises was to thwart aerial reconnaissance and air attacks.
Another official warned Iran would retaliate with a missile strike on Tel Aviv, if it was attacked by Israel.
Iran is under intense pressure over its nuclear programme, which critics say is intended to produce nuclear weapons.
The US and Israel have not ruled out the prospect of a military attack to prevent Iran developing nuclear bombs. Iran insists its programme is peaceful.