Iran said on Thursday that new U.S. sanctions were a violation of its nuclear deal with world powers, piling pressure on President Hassan Rouhani as he starts his second term. Mr. Rouhani vowed to keep up his efforts to end Iran’s isolation as he was sworn in by the Islamic Republic’s supreme leader Ayatollah Ali Khamenei following his re-election in May. “We believe that the nuclear deal has been violated and we will react appropriately,” Deputy Foreign Minister Abbas Araghchi said. “We will certainly not fall into the trap of U.S. policy and Trump, and our reaction will be very carefully considered.”

The mounting crisis creates a difficult situation for Mr. Rouhani, a 68-year-old moderate who won a second four-year term largely thanks to his efforts to repair relations with the West.

“We will never accept isolation,” Mr. Rouhani said as he was sworn in in front of top political and military officials.

Mr. Khamenei took a tougher line, saying Iran must not fall for Washington's “tricks”. “The enemy's hostility has made us more resistant," the supreme leader said.