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(Mass Communication Specialist 1st Class Adam C. Stapleton/U.S. Navy/Reuters)

The standoff in the Persian Gulf may seem like a battle between Washington and Tehran. However, if the situation worsens, U.S. allies are at risk of becoming a focal point in the dispute. At worst, they could become collateral damage.

On Thursday, it was the Brits who found themselves in troubled waters as a British tanker transited the Strait of Hormuz, a waterway used for much of the world’s oil shipments. According to the British government, Iranian vessels tried to block entry to the strait, prompting a British naval escort, the HMS Montrose, “to position herself between the Iranian vessels” and the ship.

The Iranian government has denied any confrontation, but the incident comes at a tense time in the gulf. A little over a year after the United States pulled out of the nuclear deal with Iran and other world powers, Tehran this month began to exceed the deal’s limit on uranium enrichment. The move has relatively little practical effect but is a symbolic blow to diplomacy.

The shipping routes along Iran’s gulf coast, however, provide the potential for real world conflict. A number of tankers in the Gulf of Oman have been damaged in recent months in possible sabotage attacks. When Iran shot down an unmanned U.S. surveillance drone in June, the United States even drew up plans for a retaliatory attack.

The escalation of tensions between Iran and Britain began when British forces assisted local law enforcement in apprehending an Iranian supertanker in the Mediterranean Sea near the British territory of Gibraltar on July 4. The British government later asserted that the vessel was violating E.U. sanctions on trade with Syria.

A dispute between Britain and Iran would be welcomed by the Trump administration, which has struggled to convince European nations that its hard line on Iran is necessary. “Excellent news,” White House national security adviser John Bolton tweeted last week when Britain detained the Iranian tanker.

But Britain has reason to guard against a worsening of the situation. Amid political crises at home, the country has tried to stay in the Iran deal along with other European powers. Unlike the United States, Britain has not grown less reliant on oil and gas from the Middle East in recent years but more.

Britain isn’t the only nation concerned about whether the United States has its back. Even among Middle Eastern nations deeply hostile to Iran, there is a worry: What might we be getting ourselves into?

Saudi Arabia and the United Arab Emirates have spent a lot of time, effort and money in a bid to influence the Trump administration’s view of Iran. Generally, they are relieved to have found a White House that had clearly picked a side after eight years of President Obama, who sought a more neutral approach to the Middle East.

But amid heightened tensions, these U.S. allies in the gulf have found themselves uncertain of how far they want to go. As The Washington Post’s Erin Cunningham reported from Dubai this week, some in the region are concerned that Trump has been publicly asking why the United States should be guaranteeing secure shipping lanes. It isn’t clear whether the gulf allies would risk going it alone.

“On the one hand, they want to demonstrate that the billions of dollars of military purchases have not gone to waste — that they can help defend themselves,” Henry Rome, a Middle East analyst at the New York-based Eurasia Group told The Post. “But they don’t want to give the impression they can defend themselves by themselves, lest they tempt Trump to pack up and go home.”

Notably, so far both Saudi and Emirati officials have offered relatively muted responses to alleged Iranian attempts at disruption of commerce in the gulf.

“We need to address Iran’s behavior clearly, but at the same time not to be baited into crisis,” UAE Minister of State for Foreign Affairs Anwar Gargash said in an interview with Bloomberg Television after tankers were damaged in May. “This is the region we live in and it’s important for us that we manage this crisis."

Saudi Arabia and the UAE must have been alarmed too when they saw Trump host the leader of rival gulf state Qatar, Sheikh Tamim bin Hamad al-Thani, at the White House this week. Qatar is closer to Tehran than it has been in years but faces little pushback from Washington.

It’s easy to discern what most countries involved in the crisis want right now. Iran wants sanctions lifted on its own terms. European allies want to remain in the Iran deal and keep tensions down. Even countries such as Saudi Arabia and the UAE have a reasonably understandable aim of combating Iran’s influence in the region without resorting to war.

But the inscrutable aims of the United States leave everyone else at a loss. Some members of Trump’s administration have advocated regime change in Iran, while others say they want the United States to stay in the nuclear deal.

The evidence suggests that Trump is open to a new agreement: Last month, he said the United States could be Iran’s “best friend” in the future. However, while it’s obvious he doesn’t like the Obama-era nuclear deal, it isn’t clear what could replace it, and there are few signs that Tehran is willing to acquiesce to Trump’s demands.

Meanwhile, a campaign of "maximum pressure” remains: U.S. sanctions on Iran are putting a real squeeze on the country, while Iranian Supreme Leader Ayatollah Ali Khamenei has been specifically targeted in a symbolic blow to his political legitimacy. With Iranians increasingly desperate, they may resort to more brinkmanship. Though Trump called off plans to respond militarily to Iran’s downing of a drone last month, he might change his mind in the future.

Allies have been left in the middle, even as they are alienated by a Trump administration that insults them and courts their rivals. For Britain, it’s a particularly risky position. With its ships harassed, it may need to send another warship to the gulf for protection duties. Kim Sengupta wrote in the Independent that more military hardware in the region will add to the risk of violence.

It’s “the law of unintended consequences,” Sengupta wrote, and “a scenario British government insists it wants to avoid.” It may not be able to.

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