Iran's foreign ministry said Tuesday it would take time to resume ties with Britain severed in the aftermath of an attack on the British embassy in Tehran in 2011.
"We received the letter from British Prime Minister" David Cameron who expressed the "desire for a resumption of ties," ministry spokesman Abbas Araqchi said.
But "these issues need time and negotiations on an expert level," he told a news conference, adding that "it must be decided whether their approach and behaviour have changed".
Signup to our newsletter and follow us on Facebook and Twitter!
Britain ordered Iran's embassy in London to shut after closing its own in Tehran following the storming of the compound by hundreds of Islamist students in November 2011.
They were demonstrating in front of the British embassy to express anger over new Western sanctions adopted against Tehran over its disputed nuclear drive.
Britain was one of the first European countries to adopt sanctions against the Iranian central bank to put pressure on Tehran over its nuclear programme.
Since then, both sides have said they would like to restore the ties.
Oman now represents Iranian interests in Britain, while Sweden has taken on similar responsibilities in Tehran.