DUBAI, United Arab Emirates (Reuters) -- Iran’s possible response to new U.S. sanctions could “not be pleasant,” its foreign minister said Sunday, raising the prospect of tit-for-tat retribution against the Islamic Republic’s old adversary weeks ahead of fresh nuclear talks.

Iranian leaders reacted with dismay to Friday’s announcement that Washington was going to penalize a number of Iranian and other foreign companies, banks and airlines for violating sanctions against Tehran, most of which are tied to a decade-old dispute about its nuclear program.

Washington said the moves were a signal there would be no let-up of sanctions while international talks were under way to ease the economic measures in exchange for Iran’s agreement to curb its nuclear activities. Iran has repeatedly maintained its nuclear program is for civilian ends only and denied allegations made by the West that it may want to develop nuclear weapons.

President Hassan Rouhani said Saturday the new curbs were unconstructive and against the spirit of the talks, although he added he was not pessimistic.

Foreign Minister Mohammad Javad Zarif said at a news conference Sunday that Iran would respond to the sanctions “if deemed necessary,” according to state news agency IRNA. “We can take actions that would be unpleasant to the other side,” he added, without elaborating on what those actions might be.

Zarif said the sanctions had been implemented to appease “pressure groups in the U.S. that are against any nuclear deal,” using a phrase Iranian officials normally invoke to refer to Israeli interest groups.

The U.S., Russia, Germany, France, China and Britain want Iran to scale back its nuclear program. Iran has countered it is entirely peaceful and wants sanctions lifted quickly.

Iran and the other six countries are set to resume nuclear talks in mid-September on the sidelines of the annual United Nations General Assembly meeting in New York.

The parties failed to meet an earlier self-imposed July 20 deadline for a comprehensive accord and decided to prolong the talks until Nov. 24.

(Reporting by Michelle Moghtader; Editing by William Maclean and Raissa Kasolowsky)