Philip Hammond is to visit Iran as the UK reopens its embassy for the first time since it was attacked by a mob in 2011.
The recent nuclear deal accelerated a thaw in diplomatic relations with Tehran and opened the door to the first such visit to the country by a British foreign secretary since 2001.
A senior Government source confirmed that Mr Hammond would fly out to the country over the weekend with a delegation of business leaders and senior officials.
It is the latest in a rush of missions by his international counterparts as Western allies all seek to take advantage of the improved atmosphere.
The embassy was closed almost four years ago after it was ransacked by a mob protesting against the imposition of international sanctions.
Some will be lifted in return for assurances that Iran’s nuclear programme is not aimed at producing a weapon under the deal struck by the UK and five other nations in July.
The reopening of the embassy has been plagued by technical obstacles for more than a year since it was first proposed publicly by Mr Hammond’s predecessor William Hague.
Tehran’s reluctance to relax import laws has slowed the replacement of communications and other equipment taken out when the post was abandoned.
And the Home Office sought assurances over visa regulations amid fears that it would otherwise be unable to deal with Iranians who overstayed their right to be in the UK.
The Home Office made clear that the visa issue was yet to be resolved.