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An interim deal on nuclear power with Iran would involve limited, proportionate sanctions relief, the Foreign Secretary has said.
William Hague said the "complex and detailed discussions" with Iran could still reach a resolution, but that the UK would not lift all existing sanctions at once.
He also confirmed that the newly-appointed non-resident charge d'affaires would visit Iran next month.
The next round of talks begin on 20th November.
Britain said on Monday it had revived diplomatic relations with Iran and appointed a non-resident charge d'affaires, two years after an angry mob ransacked the British embassy in Tehran.
The announcement reflects a thaw in relations with the West and comes after Iran and six world powers, including Britain, came close to a preliminary agreement about Tehran's nuclear programme at the weekend.
Britain's Foreign Office said Ajay Sharma, currently the head of the ministry's Iran department, will take up the post immediately.
US Secretary of State John Kerry has said the major powers were unified on an Iran nuclear deal during talks in Geneva at the weekend but the Iranians were unable to accept it.
Speaking to reporters in Abu Dhabi today, Mr Kerry said they were unified on Saturday when the proposal was presented to the Iranians.
He said: "The French signed off on it, we signed off on it." But he added that Iran was not able to accept the deal "at that particular moment".
US Secretary of State John Kerry has told a news conference that talks on Iran are "not a race" to complete just any agreement on the country's nuclear programme.
He added that the US hopes to reach a deal with Iran "within the next months" and that he was confident the agreement would "protect Israel".
Marathon talks between the P5+1 - the United States, Russia, China, Britain, Germany and France - and Iran on Saturday did not end in an agreement. The sides arranged to meet again on Nov. 20.
France's foreign minister said on Monday he was hopeful a deal could be reached with Iran over its nuclear programme, although Tehran still had to make an effort on a few points.
"We are not far from an agreement with the Iranians, but we are not there yet," Laurent Fabius told Europe 1 radio.
Some diplomats accused France of grandstanding during talks in Geneva at the weekend, something Fabius denied, saying Paris was not isolated, but had an independent foreign policy.
Read more: Hague confident of Iran deal
Israeli Prime Minister Benjamin Netanyahu took his case against the nuclear accord with Iran directly to the US public today, appearing on American TV to decry a "very bad deal" he feared the Obama administration was pursuing.
On CBS television's Face the Nation on Sunday, Mr Netanyahu said the proposed interim agreement, as "described to us by American sources", would have allowed Iran to maintain its capability to enrich material for nuclear bombs.
"Not a good idea, not a good deal - a very bad deal," he said, adding that the Iranians "get the hole in the tire of the sanctions and the air begins to come out".
UN nuclear agency chief Yukiya Amano said he hoped his talks with Iranian officials in Tehran on Monday would yield concrete results to help advance a long-stalled investigation into the Islamic state's atomic activities, according to Reuters.
The Islamic Republic and six world powers failed to reach a deal on Saturday during broader diplomatic talks in Geneva aimed at easing international fears over the country's nuclear programme.
"I hope the coming meeting will produce concrete results on how ... to resolve all outstanding (issues) to ensure that (Iran's) nuclear programme is exclusively for peaceful purposes," Amano, director general of the International Atomic Energy Agency (IAEA), told reporters.
The Foreign Secretary William Hague has said that he is confident a deal can been done over Iran nuclear programme in the next few weeks.
He told the BBC's Andrew Marr show: "On the question of will it happen in the next few weeks, there is a good chance of that.
"A deal is on the table and it can be done. But it is a formidably difficult negotiation, I can't say exactly when it will conclude."
Iran and six world powers failed after three days of talks to agree a deal to curb Tehran's nuclear programme.
Iran's president Rouhani says the nation has acted rationally, logically and tactfully during nuclear negotiations, according to the ISNA news agency.
But he added: "We have said to the negotiating sides that we will not answer to any threat, sanction, humiliation or discrimination.
"For us there are red lines that cannot be crossed. National interests are our red lines that include our rights under the framework of international regulations and (uranium) enrichment in Iran", he added.
Mr Rouhani also said that economic sanctions were harmful to the countries imposing them, not just Iran.
On Saturday, Iran and six world powers failed in talks to agree a deal to curb Tehran's nuclear programme but said differences had narrowed and they would resume negotiations in 10 days.
A day after nuclear talks, Iran's president Hassan Rouhani has said the nation will not bow its head to any threat or sanction against it, according to the ISNA news agency.
Latest ITV News reports
Israeli's Prime Minister said ahead of talks with John Kerry that he "utterly rejects" the "bad deal" he said was in the making over Iran.