VOA Persian's Katherine Ahn contributed to this report.
Iran is demanding that Britain release an Iranian oil tanker seized last week off the coast of Gibraltar and accused Britain of playing a "dangerous game" in the Persian Gulf region.
Iranian Foreign Ministry spokesman Abbas Mousavi told state news agency IRNA on Friday the seizure of the tanker "has consequences" and that Britain's "legal pretexts for the capture are not valid."
Mousavi's remarks came two days after Iranian President Hassan Rouhani also warned Wednesday that Britain would face unspecified "consequences" for the seizure of the vessel on suspicion of transporting oil to Syria in violation of European Union sanctions.
Tensions in the region further escalated Thursday when Britain said Iranian three military vessels tried to "impede the passage" of a British oil tanker through the Strait of Hormuz.
A British government statement said three Iranian vessels were involved in the incident, and they backed off when they received a verbal warning from a British warship. The government said Friday it would deploy the HMS Duncan warship to the Gulf to replace the HMS Montrose, which Britain says was forced to fend off the Iranian vessels.
Iran's Islamic Revolutionary Guard Corps (IRGC) has denied Britain's accusation. A statement carried by the semi-official Fars news agency Thursday said IRGC navy boats carried out normal duties and had "no clashes with alien boats, especially English boats."
Vice Admiral Jim Malloy, Commander of U.S. Fifth Fleet,which operates in the region, said in a statement late Thursday that the fleet is aware of IRGC's “unlawful harassment and attempts to interfere with the passage” of British vessel on July 10 and that the U.S. continues “to work with the Royal Navy, along with all our regional and global partners who share in our commitment to preserving and defending the free flow of commerce and the freedom of navigation.”
Tensions between Iran and the U.S. and its allies have heightened since last year, when Washington stepped up economic sanctions against Tehran and moved to stop its oil exports as a part of a "maximum pressure" policy to force Iran to end behaviors deemed to undermine regional security.
Tensions began to grow in May 2018 when U.S. President Donald Trump withdrew from a 2015 agreement between Iran and world powers that gave Tehran sanctions relief in return for containing its nuclear program. Trump rejected the deal negotiated by his predecessor Barack Obama as too weak on Iran. In response, Iran recently exceeded uranium enrichment limits in breach of the agreement.
British Defense Minister Penny Mordaunt said Britain is concerned about Thursday's disputed incident and urged Iran to "de-escalate the situation."
China and Russia, both signatories to the Iran nuclear deal, also called for restraint.
The Strait of Hormuz is a strategic waterway that is the path to market for much of the Middle East's oil.
In a Thursday interview with VOA Persian, John Hannah, a senior counselor at the Washington-based Foundation for Defense of Democracies, said he believes Iran is trying to spark a shipping crisis in the region. Iranian action could "make it so risky to ship oil through the Persian Gulf, that the price of insurance being provided to those tankers goes up so much that it will have a dramatic impact on the price of oil and the overall international economy," Hannah said.
Earlier this week, U.S. Joint Chiefs of Staff Chairman Marine General Joseph Dunford said Washington hopes to enlist allies over the next few weeks in a military coalition to safeguard strategic waters off Iran and Yemen. Washington has accused Iran of involvement in bomb attacks on six foreign oil tankers in the Gulf since May, a charge Tehran denies.
Barbara Leaf, who served as U.S. ambassador to the United Arab Emirates from 2014 to 2018, told VOA Persian that Iran's alleged harassment of the British oil tanker could prompt other countries to join the proposed U.S. naval coalition in the region. Leaf, a senior fellow at the Washington Institute for Near East Policy, cited India's decision last month to send two warships to the Gulf of Oman to protect Indian merchant vessels passing through the increasingly tense area.
"It's prudent to thicken defenses for commercial shipping not just through the Strait of Hormuz, the most critical choke point for global energy supplies, but also for the Bab-el-Mandeb strait, the choke point at the southern end of the Red Sea. Thickening defenses also is a deterrent against further attacks," Leaf said. "But the other piece that really is required here is de-escalation and diplomacy to drive toward direct discussions and eventually negotiations," she added.