NEW YORK (VINnews) — The U.S. Department of Defense has prepared a list of potential targets in Iran if Trump decides to resume the war. Officials told NBC that it would be more difficult to reach these targets than previous ones due to concealment and the constant movement of missile systems.

If President Donald Trump decides to resume military operations, identifying and striking these targets would likely prove more challenging than earlier actions, the report noted.

Meanwhile, two U.S. officials told The New York Times that American military strikes on targets in southern Iran on Monday were carried out after intelligence analysts detected a series of Iranian military activities that could have posed a threat in the 24 hours leading up to the strikes.

U.S. fighter jets reportedly sank two fast boats belonging to Iran’s Islamic Revolutionary Guard Corps that were attempting to lay mines in the Strait of Hormuz, a vital waterway through which, before the war, about one-fifth of the world’s daily oil and gas supply passed.

The officials, who spoke on condition of anonymity, also said that Iran launched drones near or around U.S. Navy warships operating in the Gulf of Oman and the Arabian Sea. Those ships are enforcing a blockade on vessels attempting to enter or exit the area.