Jeremy Hunt is to launch a fresh diplomatic bid to prevent the Iran nuclear deal unravelling and to ease tensions in the Gulf.
The Foreign Secretary will travel to Brussels on Monday for a meeting of EU foreign ministers to seek support from the European signatories to the agreement – France and Germany.
Speaking as he prepared to board a flight to Belgium, Mr Hunt said the Iran nuclear deal is not dead yet.
He added: "We are totally committed to keeping the Middle East denuclearised.
"If Iran acquires nuclear weapons then other countries in the region will acquire nuclear weapons.
"It becomes a very, very toxic and dangerous situation...
"We are looking to find a way to preserve the nuclear deal.
"Iran is still a good year away from developing a nuclear weapon.
"We think there is still some closing but small window to keep the deal alive."
Ahead of the visit, Mr Hunt also tweeted that he wanted to reduce tensions over the seizure of the Grace 1 Iranian supertanker which is being held in Gibraltar after being detained in an operation involving British Royal Marines, but hinted that Iran would face consequences if it did not abide by the terms of the nuclear deal.
He said: "Heading to Brussels for urgent talks on how to reduce tensions with Iran.
"Their approach to Mid East has been profoundly destabilising but we want to reduce not raise tensions over Grace 1 and avoid a nuclearised region.
"But a deal is a deal and if one side breaches it..."
In a joint statement ahead of the meeting, the three European powers said they were “deeply troubled” by recent events in the region and urged the US and the Iran to draw back from conflict.
“We believe the time has come to act responsibly and seek a path to stop the escalation of tensions and resume dialogue,” the statement said.
“The risks are such that it is necessary for all stakeholders to pause and consider the possible consequences of their actions.”
On Saturday, Mr Hunt spoke with his Iranian counterpart and offered to help secure the release of Grace 1.
In a telephone call with Mohammad Javad Zarif, Mr Hunt sought to reassure him the vessel was intercepted over suspicions it was carrying oil to Syria – and not because it was Iranian.
He said he had offered to facilitate the tanker’s release in return for guarantees from Tehran that it would not breach EU sanctions on the Assad regime.
The move comes amid heightened tensions in the Gulf following Donald Trump’s decision to unilaterally withdraw the US from the nuclear deal.
Last week, a Royal Navy warship intervened to drive off Iranian patrol boats after they approached a British tanker as it sailed through the Strait of Hormuz.
It prompted fears the Iranians were trying to seize a UK ship in retaliation for the detention of the Grace 1.
It was the latest in a series of incidents in the region prompting fears of a slide into all out conflict.
In recent weeks, the US has sent thousands of troops, an aircraft carrier, nuclear-capable B-52 bombers and advanced fighter jets to the Middle East.
Iran, meanwhile, has begun exceeding limits on uranium enrichment agreed in the 2015 deal amid frustration in Tehran at the return of crippling US economic sanctions.
While the Europeans say they still support the agreement – which lifted sanctions in return for Iran curbing its nuclear programme – in practice they have found it difficult to get round the US measures.
Ahead of the meeting, the US the EU foreign ministers to take a tougher stance on Iran.
Gordon Sondland, the US ambassador to the EU, said: "I think that the time for reflection is over. I think it's time to act, and by acting, I mean that our European friends should join the US in unequivocally condemning Iran's actions with respect to their malign activities, not just in the Strait of Hormuz but throughout the world, and bring them back to the table to discuss a comprehensive negotiation over all of their activities including currently being the world's lead state sponsor of terror, plotting attacks in Europe, their missile development programme and their general Middle East aggression."
On BBC Radio 4's Today programme he dismissed as "complete nonsense" an assessment by Sir Kim Darroch that Donald Trump decided to pull out of the Iran nuclear deal in an act of spite because it was agreed by his predecessor Barack Obama.
Sir Kim resigned as UK ambassador to Washington after his sensitive diplomatic dispatches were leaked and Mr Sondland said Mr Trump's approach to the Iran deal had been "very, very thoughtful".
Ahead of the meeting in Brussels, Mr Hunt said: “The Middle East is already one of the most unstable regions in the world, but if the different parties were armed with nuclear weapons it would represent an existential threat to mankind. I will do everything in my power to prevent that from happening.
“I’ll be building on the leadership shown by the UK, alongside France and Germany, as we do what it takes to maintain the nuclear deal, and to work to encourage Iran back into compliance.”
At the same time Mr Hunt stressed the importance of maintaining freedom of navigation in the Gulf.
“Following the brave work of our Royal Navy in the Persian Gulf we will work with partners to maintain the right of commercial ships to go about their rightful business,” he said.