TEHRAN, Iran — Iran's president says U.S. financial sanctions on Iran's foreign minister are "childish" and a barrier to diplomacy.

Hassan Rouhani's remarks Thursday came after the Trump administration announced it imposed financial sanctions on Foreign Minister Mohammad Javad Zarif as part of its escalating campaign of pressure against the Islamic Republic.

The highly unusual action of penalizing another nation's top diplomat followed President Donald Trump's executive order placing sanctions on Iran's supreme leader, Ayatollah Ali Khamenei.

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Rouhani says the U.S. has "started doing childish things."

He says U.S. officials "claim to want to negotiate with Iran, without any pre-conditions . and then they put sanctions" on Zarif.

Tensions have escalated in the Persian Gulf region since Trump's withdrawal last year from the 2015 nuclear deal with Iran and re-imposition of new sanctions.