DUBAI -- Iran's possible response to new U.S. sanctions could "not be pleasant", its foreign minister said on 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 that there would be no let-up of sanctions while international talks were underway to ease the economic measures in exchange for Iran's agreement to curb its nuclear activities..

Iran says its nuclear program is for civilians ends only and denies allegations from the West that it may want to develop nuclear weapons.

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

On Sunday, Foreign Minister Mohammad Javad Zarif told a news conference 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.

Zarif did not elaborate on what the measures might be.

He added that 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 United States, France, Germany, Russia, China and Britain want Iran to scale back its nuclear program. Iran says it is entirely peaceful and wants sanctions lifted quickly.

Iran and world powers - the United States, France, Germany, Britain, Russia and China - are set to resume nuclear talks in mid-September on the sidelines of the annual U.N 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.