Tehran and world powers failed to clinch a long-sought deal yesterday despite marathon talks in Geneva but kept hopes alive by agreeing to meet again in the Swiss city on November 20.
Hague said in a statement to parliament on the talks, which he attended, that there was "no doubt in my mind" that a deal could be reached.
"Our aim is to produce an interim, first-step agreement with Iran that can then create the confidence and the space to negotiate a comprehensive and final settlement," Hague said.
Hague said that "any interim agreement would involve offering Iran limited, proportionate sanctions relief".
But he said that the international community would be "vigilant and firm" in upholding sanctions until there was an interim deal with Iran.
Hague meanwhile confirmed the reestablishment of diplomatic ties between Britain and Iran following the ransacking of the British embassy in Tehran, with both countries today naming non-resident envoys to each other's capital.
"It's not right to speak of any veto on the negotiations by any of the E3+3 countries," he said, referring to the world powers involved in the talks.
"The position put to Iran by all of us together in the final hours had been amended in the light of comments by various countries... But it was a completely united position."
He said the common position gave an "extremely strong foundation for the next round of talks on November 20.
