The shift could drastically alter the balance of power in the region, and risks alienating key U.S. allies such as Saudi Arabia and United Arab Emirates who are central to the coalition fighting Islamic State. Sunni Arab leaders view the threat posed by Shiite Iran as equal to or greater than that posed by the radical group Islamic State, also known as ISIS or ISIL.
Israel contends the U.S. has weakened the terms of its negotiations with Iran and played down Tehran’s destabilizing role in the region.
Over the past decade, Washington and Tehran have engaged in fierce battles for influence and power in Iraq, Syria, Lebanon and Afghanistan fueled by the U.S. overthrow of Iraqi strongman Saddam Hussein and the Arab Spring revolutions that began in late 2010. U.S. officials still say the option of military action remains on the table to thwart Iran’s nuclear program.
Iran's Foreign Minister Javad Zarif, left, meets with U.S. Secretary of State John Kerry, far right, in Vienna. ENLARGE
Iran's Foreign Minister Javad Zarif, left, meets with U.S. Secretary of State John Kerry, far right, in Vienna. Jim Bourg/Press Pool
But recent months have ushered in a change as the two countries have grown into alignment on a spectrum of causes, chief among them promoting peaceful political transitions in Baghdad and Kabul and pursuing military operations against Islamic State fighters in Iraq and Syria, according to these officials.
The Obama administration also has markedly softened its confrontational stance toward Iran’s most important nonstate allies, the Palestinian militant group Hamas and the Lebanese militant and political organization, Hezbollah. American diplomats, including Secretary of State John Kerry , negotiated with Hamas leaders through Turkish and Qatari intermediaries during cease-fire talks in July that were aimed at ending the Palestinian group’s rocket attacks on Israel, according to senior U.S. officials.
U.S. intelligence agencies have repeatedly tipped off Lebanese law-enforcement bodies close to Hezbollah about threats posed to Beirut’s government by Sunni extremist groups, including al Qaeda and its affiliate Nusra Front in Syria, Lebanese and U.S. officials said.
"This shows that although we see Turkey and Arab states as our closest allies, our interests and policies are converging with Iran’s,” said Vali Nasr, dean of the School of Advanced International Studies at Johns Hopkins University and a former Obama administration official. "This is a geostrategic reality at this moment, more than a conscious U.S. policy.”
Obama administration officials stressed they’re not directly coordinating their regional policies or the war against Islamic State with Iran. They also said pervasive U.S. economic sanctions remain in place on Tehran, Hamas and Hezbollah.
Still, these officials said the intensive negotiations the U.S. has pursued with Iran since last year on the nuclear issue could help stabilize the Mideast and have improved understanding.
"The world is clearly better off now than it would have been if the leaders on both sides had ignored this opening,” Wendy Sherman, the lead U.S. negotiator with Iran, said last week.
Iranian officials, including President Hasan Rouhani, have said there could be more cooperation with the U.S. in the war on Islamic State, but only if a nuclear accord is reached.
Administration critics, including Israel and Arab states, see the White House as determined to seal a deal with Iran as a monument to President Barack Obama’s foreign policy record.
"The Iranian regime is revolutionary and can’t get too close to us. So I’d be wary of any rapprochement,” said Scott Modell, a former Central Intelligence Agency officer now at the Center for Strategic and International Studies in Washington. "I think they are hell bent on pursuing a number of courses that run counter to U.S. interests.”
Iraq has been at the center of a regional proxy war between the U.S. and Iran since the George W. Bush administration invaded Baghdad in 2003.
Since the U.S. resumed military operations inside Iraq in August, however, the Revolutionary Guard, or IRGC, has explicitly ordered its local proxies not to target American military personnel conducting and coordinating attacks against Islamic State from bases around Baghdad and Iraq’s Kurdish region, according to U.S. officials who have tracked Iranian communications.
Gen. Qasem Soleimani, the commander of the Guard’s overseas operations known as the Qods Force, specifically instructed Iraqi Shiite militias long at war with the U.S., such as the Mahdi Army and Kata’ib Hezbollah, that American efforts to weaken Islamic State were in the long-term interests of Tehran and its allies, said these officials.
Meanwhile, the U.S. military is planning to play down and avoid publicity for the annual minesweeping exercise being organized by U.S. Navy’s Fifth Fleet. In past years, the exercise has been used to highlight unified opposition to Iranian activities in the Persian Gulf, according to a U.S. official.
Some officials say de-emphasizing deterrence against Iran could be destabilizing, signaling to the Revolutionary Guard that the U.S. isn't going to take steps to counter their measures.
However, the U.S. now has gone beyond the use of signals. American officials said the Obama administration has passed messages to Tehran by using the offices of Iraq’s new Shiite prime minister, Haider al-Abadi, as well as Grand Ayatollah Ali al-Sistani, one of Shiite Islam’s most senior clerics.
The U.S. has also made it clear to Tehran that its stepped-up military strikes against Islamic State targets in Syria won’t be turned on forces loyal to Syrian President Bashar al-Assad, according to U.S. officials.
Mr. Assad is Iran’s closest Arab ally. And the Revolutionary Guard and Gen. Soleimani have mobilized Iranian military personnel and Lebanese and Iraqi Shiite militiamen to fight inside Syria in support of the Damascus regime. Any U.S. strikes on Mr. Assad’s security forces could end up hitting Iranian or Hezbollah soldiers and military advisers, sparking a broader conflict, U.S. and Arab officials said.
"They [the U.S.] want to focus on ISIL and they are worried about antagonizing the Iranians, which they say may cause them to react or the militias in Iraq to react against our embassy and interests in Iraq and derail the [nuclear] talks,” said a senior U.S. defense official working on Iraq. "They are articulating in high-level interagency meetings that they don’t want to do anything that’s interpreted by the Iranians as threatening to the regime.”
The détente that has taken hold is filtering into other theaters of traditional American-Iranian conflict, said U.S. and Arab officials.
Washington for years has sought to weaken Hezbollah’s political and military power in Lebanon through sanctions and the backing of rival political parties in Beirut. But the threat posed by Islamic State, Nusra Front and other Sunni extremist groups to Lebanon has changed the security dynamics there, said U.S. and Arab officials.
U.S. intelligence agencies on a number of occasions have provided tips on terrorist threats to Lebanese security agencies that are known to be close or under the sway of Hezbollah, said U.S. and Arab officials. Among them is the intelligence unit, known as the General Security Directorate, which has arrested Nusra Front cells in Beirut and northern Lebanon over the past two years.
The Obama administration’s indirect diplomatic engagement with Hamas has unnerved Israel and allied Arab states. Washington maintains a policy of no direct talks with the Palestinian group, which is designated a terrorist organization by the U.S. and European Union. But Mr. Kerry and other U.S. officials regularly conveyed messages to Hamas’s political chief, Khaled Meshaal, through Qatari and Turkish diplomats during cease-fire talks this summer.
Israeli and Arab officials argued this engagement strengthened Hamas’s profile at the expense of the Palestinian leadership led by Mahmoud Abbas.
The regional truce playing out between Washington and Tehran is fragile and could easily be reversed, said U.S., Arab and Iranian officials.
The two sides have set a late November deadline to conclude a comprehensive agreement aimed at curtailing Iran’s nuclear program in exchange for an easing of Western sanctions. U.S. officials say the prospects for the accord remain only 50/50 and that tensions between the two sides could quickly ratchet up in the wake of a diplomatic failure.
"There is no question that, if everything goes away, escalation will be the name of the game on all sides, and none of that is good,” Ms. Sherman said last week.