Borrell's trip, his first to Iran since taking office, follows a spike in tensions between arch foes Washington and Tehran following the January 3 assassination in Baghdad of a top Iranian general in a US drone strike.

The two-day visit opened with a meeting with Foreign Minister Mohammad Javad Zarif, ahead of talks with President Hassan Rouhani and parliament speaker Ali Larijani.

The 2015 nuclear deal between Tehran and a group of world powers has been crumbling since US President Donald Trump withdrew from it in 2018, and Washington has since stepped up sanctions and a campaign of "maximum pressure" against Iran.

Tehran has gradually stepped back from its own commitments under the deal, while military tensions with the US brought the two countries to the brink of full-blown confrontation last month.

Borrell's mission aims "to de-escalate tensions and seek opportunities for political solutions to the current crisis," said the office of the EU's high representative for foreign affairs and security policy.

The trip will allow Borrell "to convey the EU's strong commitment to preserve" the nuclear deal, known as the Joint Comprehensive Plan of Action, and to discuss cooperation between the EU and Iran, his office said.

Iranian foreign ministry spokesman Abbas Mousavi told a press conference Monday that Tehran hoped Borrell's visit would help the European Union "understand" Tehran's situation and prompt the bloc to "show goodwill by taking serious measures".