Iran’s supreme religious leader, Ayatollah Ali Khamenei, declared that President Obama’s new nuclear strategy amounted to “atomic threats against Iranian people,” and Iranian state television reported Thursday that the military had begun a large exercise in the Persian Gulf, where the United States and Israel have both increased their presence in recent months.

The ayatollah’s statement on Wednesday referred to the section of Mr. Obama’s “Nuclear Posture Review” that guaranteed non-nuclear nations that they would never be threatened by a United States nuclear strike — as long as they are in compliance with the Nuclear Nonproliferation Treaty as judged by the United States.

Speaking in Washington on Wednesday, Gary Samore, Mr. Obama’s top adviser on unconventional weapons, said the wording of the nuclear review was “deliberately crafted” to exclude Iran and North Korea from the security guarantee, creating an incentive for both countries to come into compliance with the treaty. (While North Korea has conducted two nuclear tests and is believed to have fuel for eight or more weapons, the United States has never acknowledged it as a nuclear-weapons state.)

Mr. Samore insisted that Mr. Obama’s decision did not amount to making a nuclear threat against Iran, which many Western countries believe is pursuing a weapon. The policy, Mr. Samore said, referred only to the use of nuclear weapons in the most extreme circumstances, which most experts believe means in retaliation for a strike against the United States or its allies.