Five world powers will hold talks with Iran later this month as they work to save a 2015 nuclear accord amid rising tensions in the Persian Gulf.
Britain, France, Germany, Russia and China will meet Iran in Vienna on July 28 to discuss the Joint Comprehensive Plan of Action (JCPOA), the agreement's formal name, the EU's foreign policy service said in a statement on July 23.
"The meeting has been convened at the request of France, Germany, the United Kingdom, and Iran, and will examine issues linked to the implementation of the JCPOA in all its aspects," the statement said.
Under the deal, which initially included the United States, Tehran had initially promised to greatly limit its nuclear program in exchange for sanctions relief.
Last year, U.S. President Donald Trump pulled out of the deal and reimposed economically crippling sanctions in many sectors, including the crucial oil and financial industries.
France, Germany, and Britain -- three of the six remaining accord signatories -- have tried to salvage the deal and have proposed a complicated financial barter system designed to provide some economic relief to Tehran.
Iran says it no longer feels bound by the accord and on July 1 said it had amassed more than the permitted amount of low-enriched uranium.
Efforts to salvage the deal have been complicated in recent weeks by escalating tensions between London and Tehran, which were triggered by the capture of an Iranian tanker off Gibraltar and Iran's subsequent seizure of a British-flagged oil tanker in the Hormuz Strait.
In a July 23 tweet, Iranian Foreign Minister Javad Zarif congratulated Boris Johnson for winning a vote to become the new leader of the Conservative Party and incoming British prime minister.
But in a sign of the tough talks that lie ahead, he also warned Tehran will "protect" its waters.
"Iran does not seek confrontation. But we have 1500 miles of Persian Gulf coastline. These are our waters & we will protect them," he wrote.
"The May govt's seizure of Iranian oil (tanker) at behest of US is piracy, pure & simple," he added.
The Vienna meeting will be chaired by the EU foreign policy service's Secretary General, Helga Schmid.