BEIRUT, Lebanon — Iranian officials reacted with unified irritation on Thursday to the Trump administration’s decision to sanction Iran’s foreign minister, calling the move petty and provocative — further evidence, they said, of Washington’s insincerity when it talks of peace.

The foreign minister, Mohammad Javad Zarif, an American-educated diplomat who negotiated the 2015 nuclear deal that President Trump rejected last year, is one of Iran’s best-known leaders and perhaps its most effective in making his country’s case to the West. The sanctions, imposed on Wednesday, could make it more difficult to engage in the new diplomacy that Mr. Trump says he wants.

With Iran and the United States locked for months on the brink of armed conflict, Iran’s leaders are often viewed as split between hard-liners who urge confrontation and moderates like Mr. Zarif who support diplomacy.

But Western analysts see the punishment of Mr. Zarif as the latest in a series of signs that the Trump administration is itself deeply divided over the right approach to Iran — and that, despite Mr. Trump’s insistence that he wants to negotiate, his most hawkish advisers are not interested in diplomacy.