Philip Hammond
Philip Hammond Flash 90

Britain will reopen its embassy in Tehran during a visit to Iran by Foreign Secretary Philip Hammond due to start on Sunday, an Iranian foreign ministry official told AFP on Thursday.

The official said Hammond, who helped negotiate the Iran nuclear deal in July, "will travel Sunday to Iran for the reopening of the British embassy."

The embassy has been closed since 2011 after it was stormed by protesters following the implementation of sanctions against the Islamic regime.

Taking part in the rioting mob were members of the Basij paramilitary brigade, which is controlled by the Iranian Revolutionary Guards. The embassy was looted, the British flag was burned, and damage was inflicted to the property.

Britain's decision to take the step that normalizes ties comes very soon after the deal, which lifts limitations on Iran in terms of its ballistic missile program even while not addressing its role as the leading state sponsor of terrorism - or its appalling human rights record.

Iran is set to gain a windfall of hundreds of billions of dollars in sanctions relief as part of the deal.

In a troubling revelation, Senators Mark Kirk (R-IL) and Marco Rubio (R-FL) sent a letter to the US State Department on Wednesday demanding the publication of letters sent by the Obama administration to foreign governments, allegedly promising that their companies won't be penalized for breaching sanctions on Iran.

Those governments include the UK, along with France, Germany and China.

According to the Senators, Congress has been made aware that in the letters the governments were promised "that their companies may not be impacted if sanctions are re-imposed in response to Iranian violations of the agreement."