The British government announced in early October that both sides agreed to appoint non-resident charge d'affaires and work toward establishing formal diplomatic ties.
The British Embassy in Tehran closed in November 2011 following an attack the British government said was the work of "government-sponsored militias." The Iranian Embassy in London closed as well.
Iranian Foreign Ministry spokeswoman Marziyeh Afkham said steps were underway to repair diplomatic ties.
"By introducing the non-resident charges d'affairs, action will be taken for reopening embassies and this is the first practical step in the reopening of embassies in London and Tehran," she said in remarks published Thursday by Iran's semiofficial Fars News Agency.
The British Foreign and Commonwealth Office said last week it was keeping some of its diplomatic channels with Iran open through social media platforms.
British Foreign Secretary William Hague has said there was "no doubt" Iran was engaging the world differently under new President Hassan Rouhani than it did under his hard-line predecessor, Mahmoud Ahmadinejad.