The renewed diplomacy included a call between the two countries’ top diplomats, demonstrating how both sides wanted to de-escalate a crisis that flared up after Gibraltar authorities and the Royal Marines seized the Grace 1 on July 4. The U.K. says the Iranian tanker was carrying 2 million barrels of oil to Syria in violation of European Union sanctions prohibiting crude sales to Bashar al-Assad’s government.
In a tweet, British Foreign Secretary Jeremy Hunt offered to return the tanker provided that Iran guaranteed its oil wouldn’t go to Syria. Gibraltar on Saturday released the four Indian seamen who manned Iran’s ship.
Mr. Hunt said he had a constructive call with Iranian Foreign Affairs Minister Javad Zarif, whom the British diplomat said had pledged to work to calm things down.
“I reassured him our concern was destination not origin of the oil,” Mr. Hunt wrote.
In a tweet posted late Saturday on Iran’s official government account, Mr. Zarif didn’t directly address Mr. Hunt’s demand of assurances that the ship’s oil wouldn’t go to Syria but said it was headed to a legal destination in the Eastern Mediterranean Sea.
Separately, Iran’s Oil Minister Bijan Zanganeh told Iranian lawmakers in Tehran that the controversy over the Grace 1 was resolvable and not complicated, according to ISNA, the Iranian news outlet.
Iranian officials have denied that the ship was carrying oil to Syria. Even if it was, Iranian officials say, Iran isn’t subject to any U.K. or European oil embargo placed on Syria.
The fight over the tanker comes amid a standoff between Iran and the U.S., which last year pulled out of a 2015 international agreement curbing Iran’s nuclear program and imposed harsh sanctions to punish Tehran for its threatening posture in the Middle East. The U.S. has built up its military presence in the Persian Gulf this year, citing Iranian threats.
Iran began retaliating in recent weeks, executing its first intentional breach of the nuclear deal’s limits on its atomic fuel and shooting down an American surveillance drone over the Strait of Hormuz. The U.S. has also accused Iran of attacking tankers in the Gulf of Oman and coordinating with allied militias to blow up oil infrastructure in Saudi Arabia—accusations that Iran denies.
The U.K. effort to calm tensions over the Grace 1 came after Iranian authorities issued threats against British shipping interests in the Persian Gulf. On Thursday, the U.K. accused Iranian boats of attempting to block a British-flagged supertanker as it was about to cross the Strait of Hormuz.
Tehran denied harassing the ship, but the accusation complicated shipping in the Persian Gulf, where U.K. authorities raised the threat level for commercial vessels and sent another warship to protect shipping lanes.
In Gibraltar, authorities said the Grace 1 will remain detained pending the end of an investigation and court process.
The ship’s captain and three crew members had been arrested on Thursday and Friday but were released Saturday, Gibraltar police said. Investigators freed the detainees before the maximum detention limit of 72 hours after concluding they wouldn’t be charged within that time frame, a person familiar with the matter said. The crew isn’t free to travel and their travel documents are with the police, the person said.
Gibraltar’s authorities said they detained the ship, arrested the crew and then released them as a matter of the law and not because of external pressure from any country.
The controversy stems from an attempt to enforce EU sanctions banning the sale of crude to Mr. Assad’s regime in Syria in 2011. The EU—to which the U.K. still belongs—alleges the fuel has helped Mr. Assad carry out human-rights violations against civilians.
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