Iran must match its new talk of improving relations with the international community with actions, William Hague has said after meeting his counterpart Mohammed Javad Zarif in New York.
The Foreign Secretary urged Iran to take "concrete steps" to address concerns over its behaviour after talks which covered the country's nuclear programme, human rights and the conflict in Syria - where it supports the regime of President Bashar Assad.
The two foreign ministers met as politicians gathered for the United Nations General Assembly (UNGA) in a sign of a possible thaw in relations with Tehran following the election of new president Dr Hassan Rouhani.
"The United Kingdom does not seek a confrontational relationship with Iran and is open to better relations," Mr Hague said after the meeting. "The United Kingdom welcomes President Rouhani and Foreign Minister Zarif's recent statements about Iran's wish to improve its relations with the outside world.
"The time is now right for those statements to be matched by concrete steps by Iran to address the international community's concerns about Iran's intentions. If such steps are taken, I believe a more constructive relationship can be created."
The talks come as tensions between Tehran and the West appeared to have eased in recent days, with Dr Rouhani saying he is ready for talks over Iran's disputed nuclear programme. Dr Rouhani, who has vowed to reach out to the world, has said his own UNGA appearance may be a chance to start a new round of nuclear negotiations.
Prime Minister David Cameron made the unusual move of writing to Mr Rouhani following his election earlier this year, expressing the hope that there could be a step-by-step improvement in relations between the two countries.
Dr Rouhani, who is seen as a moderate cleric, called for dialogue with the West after winning a landslide victory in the June 14 presidential elections.
Britain has not had a diplomatic presence in Iran since November 2011 when its embassy in Tehran was stormed by a mob, triggering one of the worst crises between the two countries since the 1979 Islamic revolution.
Mr Hague said he and Mr Zarif had agreed on the need to restart talks on the nuclear programme between Iran and the E3+3 group consisting of the United States, Russia, China, the United Kingdom, France and Germany. He added that Iran could play a "constructive role" by backing negotiations to end fighting in Syria, which is in the spotlight for alleged chemical weapons use by President Assad's forces in a conflict that has killed more than 100,000 people. Iran provides personnel, equipment, weapons and financial assistance to the regime.