Iran will respond to the European Union's "final" text by midnight on Monday, Iranian Foreign Minister Hossein Amir-Abdollahian said, calling on the United States to show flexibility for the revival of a 2015 nuclear pact. "We will need more talks if Washington does not show flexibility for resolving of the remaining issues ... Like Washington, we have our own plan B if the talks fail," he said, according to Iran's Fars news agency.

The EU, as coordinator of Iran's nuclear talks with world powers, said last week it had put forward a "final" text following four days of indirect talks between U.S. and Iranian officials in Vienna.

Washington has said it is ready to quickly reach an agreement to restore the deal on the basis of the EU proposals.

Iranian officials said last week that they would convey their "additional views and considerations" to the EU.