By Phil Stewart and Michelle Nichols

WASHINGTON/UNITED NATIONS (Reuters) – Three years ago, when Iran’s military captured 10 U.S.sailors after they mistakenly strayed into Iranian waters, U.S. Secretary of State John Kerry and Iranian Foreign Minister Mohammad Javad Zarif jumped on the phone in minutes and worked out the sailors’ release in hours.

Could a similar crisis be so quickly resolved today?

“No, Zarif said in a recent interview with Reuters. “How could it be averted?”

Zarif and the current Secretary of State, Mike Pompeo, have never spoken directly, according to Iran’s mission at the United Nations. They instead tend to communicate through name-calling on Twitter or through the media.

“Pompeo makes sure that every time he talks about Iran, he insults me,” Zarif said.  “Why should I even answer his phone call?”

The open rancor between the nations’ two top diplomats underscores growing concern that the lack of any established channel for direct negotiation makes a military confrontation more likely in the event of a misunderstanding or a mishap, according to current and former U.S. officials, foreign diplomats, U.S. lawmakers and foreign policy experts.

The Trump administration this month ordered the deployment of an aircraft carrier strike group, bombers and Patriot missiles to the Middle East, citing intelligence about possible Iranian preparations to attack U.S. forces or interests.

“The danger of an accidental conflict seems to be increasing over each day,” U.S. Senator Angus King, a political independent from Maine, told Reuters as he called for direct dialogue between the United States and Iran.

A senior European diplomat said it was vital for top U.S. and Iranian officials to be on “speaking terms” to prevent an incident from mushrooming into a crisis.

“I hope that there are some channels still existing so we don’t sleepwalk into a situation that nobody wants,” said the diplomat, speaking on condition of anonymity. “The rhetoric that we have is alarming.”

State Department spokeswoman Morgan Ortagus declined to address how the administration would communicate with Iran in a crisis similar to the 2016 incident, but said:  “When the time to talk comes, we are confident we will have every means to do so.”

The administration’s “maximum pressure campaign” against Iran, she said, aims to force its leaders to the negotiating table.

“If the Iranians are willing to engage on changing their ways to behave like a normal nation,” Ortagus said, “we are willing to talk to them.”

TWITTER DIPLOMACY

In 2016, Kerry and Zarif knew one another well from the complex negotiations to reach a 2015 pact to limit Iran’s nuclear capabilities.

Three years later, top-level diplomatic relations have all but disintegrated in the wake of the Trump administration’s withdrawal from the nuclear pact, its tightening of sanctions on Iranian oil, and its recent move to designate part of Iran’s military as a terrorist group.

U.S. military officials cite growing concern about Iran’s development of precise missiles and its support for proxy forces in Syria, Iraq, Yemen and beyond.

In the absence of direct talks, Twitter has become a common forum for U.S. and Iranian officials to trade biting barbs. On Wednesday, an advisor to Iranian president Hassan Rouhani fired off a tweet at Pompeo castigating him for provoking Iran with military deployments.

“You @SecPompeo do not bring warships to our region and call it deterrence. That’s called provocation,” the advisor, Hesameddin Ashena, tweeted in English. “It compels Iran to illustrate its own deterrence, which you call provocation. You see the cycle?”

That followed a Trump tweet on Sunday threatening to “end” Iran if it sought a fight, and a long history of bitter insults traded by Pompeo and Zarif.

Pompeo in February called Zarif and Iran’s president “front men for a corrupt religious mafia” in a tweet. That same month, another official at Pompeo’s State Department tweeted: “How do you know @JZarif is lying? His lips are moving.”

Zarif, in turn, has used the social media platform to condemn Pompeo and White House National Security Adviser John Bolton’s “pure obsession with Iran,” calling it “the behavior of persistently failing psychotic stalkers.”

‘AMERICANS HAVE OPTIONS’

U.S. officials, diplomats and lawmakers said they doubted Zarif would refuse to take a call from Pompeo in a crisis, given the risks for Iran in any conflict with the U.S. military.

In a Tuesday briefing with reporters, Pompeo appeared to dismiss concerns about Washington’s ability to communicate and negotiate with Iran.

“There are plenty of ways that we can have a communication channel,” Pompeo said.

Diplomats say Oman, Switzerland and Iraq are nations with ties to both countries that could pass messages.

“It’s a little bit like the Israelis – when they need to get messages to people, they can get messages to people,” said a second senior European diplomat.

Representative Michael Waltz – the first U.S. Army Green Beret elected to Congress, said he favored the diplomatic freeze as a way to force Iran into serious negotiations.

“If you don’t have diplomatic isolation, you’re having one-off talks, that lessens the pressure,” said Waltz, who is also a former Pentagon official.

But indirect message-passing can be too cumbersome in a fast-moving crisis, said Kevin Donegan, a retired vice admiral who oversaw U.S. naval forces in the Middle East as commander of the Fifth Fleet when the U.S. sailors were captured by Iran.

Such dealings through intermediaries “require time and will not allow an opportunity to de-escalate a rapidly unfolding tactical situation,” said Donegan, now a senior adviser at the Center for Strategic and International Studies, who added that he was not commenting on current U.S. policy.

Donegan and Waltz both said it would be helpful to have some kind of hotline between the U.S. and Iranian militaries, but Donegan and other experts were skeptical Iran would agree to such an arrangement.

BACK CHANNELS THROUGH OMAN, IRAQ & RUSSIA?

On May 3 – after Washington became alarmed by intelligence indicating that Iran might be preparing for an attack on the United States or its interests – it sent messages to Iran via “a third party,” one U.S. official said, speaking on condition of anonymity.

Marine General Joseph Dunford, chairman of the Joint Chiefs of Staff, also told Congress on May 8 that messages had been sent to “to make sure that it was clear to Iran that we recognized the threat and we were postured to respond.”

Waltz said Dunford told lawmakers at a closed-door hearing that he had sent a message to Qassem Soleimani – the influential commander of the Revolutionary Guards’ Quds Force – warning him that Iran would be held directly accountable if one of its proxy forces attacks Americans.

“The message now was: ‘We’re not going to hold your proxies accountable'” if they attack U.S. citizens or forces in the region, he said. “‘We’re going to hold you, the regime, accountable.'”

Another official said the United States had authorized Iraq “to let the Iranians know that there is no plausible deniability about attacks on Americans in Iraq” after U.S. intelligence flagged preparations for a possible attack by Iran-backed militias in Iraq.

Joseph Votel, the now retired four-star general who oversaw U.S. troops in the Middle East until March, noted earlier this year that the U.S. military might be able to indirectly get a message to Iranian forces through an existing hotline with Russia meant to avoid accidental conflicts in Syria.

“The Iranians can talk to the Russians,” he said.  “We have a well-established professional communication channel with the Russians.”

But the prospect of relying on the Russian government to get United States out of a crisis with Iran is hardly reassuring to many current and former officials in the United States.

“That would be a risky choice,” said Wendy Sherman, an undersecretary of state in the Obama administration.

(Reporting by Phil Stewart and Michelle Nichols; Editing by Brian Thevenot)