The EU’s External Action Service chief Federica Mogherini invited Iran on Monday to “reverse its steps” and go back to the 2015 nuclear deal.

Addressing the press after a foreign ministers council in Brussels, Mogherini called the 2015 “effective” in avoiding Iran’s development of a nuclear bomb, adding that “there is no alternative to this deal.”

Germany, France and Britain have called for “responsible” action to reduce tensions between Tehran and the United States in a last-ditch effort to salvage the 2015 nuclear deal with Iran.

Upon arrival at the foreign ministers’ summit in Brussels on Monday, the British foreign Secretary Jeremy Hunt noted that “Iran is still a good year away from developing a nuclear bomb,” adding that there is now a “small window to keep the deal alive.”

In a joint statement released on Sunday, the EU’s biggest economies — Germany, France, and the UK — called for conflict de-escalation, as Tehran is scaling back its obligations under the agreement, which promised sanctions relief in exchange for curbs on Iran’s nuclear programme.

Curbs include a commitment by Iran not to enrich uranium to a higher level of purity and stop stockpiling nuclear fuel. Iran is gradually moving to breach the terms of the Joint Comprehensive Plan of Action (JCPOA), as western signatories have failed to keep their own side of the deal to ease economic sanctions.

After the US Administration unilaterally withdrew from the JCPOA framework, European companies had to choose between operating in Iran or the US market. The US has threatened its own allies with secondary sanctions, forcing major French and German investors to leave Iran.

This month, Iran has moved to raise the limits on uranium enrichment, although far below the levels required for the development of a nuclear weapon. “We strongly urge Iran to reverse its recent decisions in this regard,” the European statement read on Sunday.

For its part, Iran has called on the EU to widen the scope of a barter trade mechanism that the EU has set up to circumvent US sanctions, over and beyond food and medicine. Tehran is mainly interested in oil exports and has been cautiously escalating the conflict, striving to raise the stakes for European non-compliance with the 2015 agreement.

While US sanctions do not target food and medicine, they include oil sales, even for countries heavily reliant on Iranian imports, such as India, Japan, and Turkey. Washington has been relentlessly enforcing the agreement, with heavy-handed enforcement of sanctions that included direct threats on companies investing in Iran, including Daimler, Total, and Renault.

Meanwhile, there is heightened tension between Iran and the UK, after British forces captured an Iranian tanker bound for Syria off the coast of Gibraltar. On Saturday, foreign secretary and aspirant prime minister, Jeremy Hunt, reassured Tehran that the tanker would be released as soon as it was confirmed that the tanker would not head for Syria.

Iran has denied that the tanker was ever bound for Syria and has called the incident “piracy.” Last Thursday, Iranian boats attempted to impede a British oil tanker in the Straights of Hormuz, but they were kept away by a Royal Navy ship. Iran has denied its navy has tried to take over the British tanker.