The Middle East is changing fast but the U.S. seems to be the last government to realize it and respond.

For at least 10 years, the region has been caricatured as divided into two camps: a pro-Iranian coalition and a looser but larger group that opposes Iran’s ambitions. For short, it’s sometimes foolishly reduced to a Sunni-Shiite sectarian divide.

That was always a distortion, and it’s become increasingly clear that, while the pro- and anti-Iranian camps do exist, there’s also a distinctive third bloc emerging, with a Sunni Islamist orientation, led by Turkey. Ankara is turning into a major regional player with its own agenda, ambitions, ideology and allies.

The key players in the anti-Iranian group are pro-American: Arab states like Saudi Arabia, the United Arab Emirates, Egypt, Jordan and Israel. The war in Syria unified this group with Turkey and its allies starting in 2011, in shared opposition to the Iranian-backed dictator Bashar Assad.

But when rebel-held parts of Aleppo fell to pro-Assad forces in December, 2016, the Syrian war effectively ended along with the united front against Iran. Turkey instead began to focus on containing Kurdish militias in northern Syria and forging a partnership with Russia, Iran and Assad. It no longer views Iran as an adversary, but as a rival or, sometimes, a partner.

Turkey’s role at the epicenter of a new Middle East alliance was consolidated by the 2017 boycott of Qatar by Saudi Arabia, the UAE, Bahrain and Egypt. Qatar has relied on Turkey, which maintains a military base in that country, for support against the boycott. Qatar also needs to maintain cordial relations with Iran because those countries share a natural gas field that provides Qatar with its huge per capita income.

Qatar and Turkey also back the regional Sunni Islamist Muslim Brotherhood movement, and its support for those organizations, including Hamas, was a major cause of the boycott. During the Syrian war, Hamas had to choose between its Sunni Islamist identity and its alliance with Shiite Iran and Alawite Syria, where it was headquartered. Eventually it fled Syria, abandoning assets and property.

But now, just as Turkey and Qatar are growing closer to Iran, Hamas is renewing its Iranian ties.

Israel and most pro-American Arab states view the consolidation of this Turkish-led coalition with alarm partly because it weakens the anti-Iranian camp.

Moreover, if Turkey — finally turning away from Europe after a century of unsuccessful efforts to integrate with the West — fixes its gaze eastward, it could become a regional hegemon as ambitious as Iran and more effective.

Turkey has a larger economy, more sophisticated technology and a stronger military. It also remains a member of the North Atlantic Treaty Organization. Turkey isn’t as disruptive as Iran, but could become so, or at least as domineering, over the long run.

Turkey has not hidden its growing ambition to revive the dominance that the Ottoman Empire enjoyed over much of the Islamic world. At a recent rally, Turkish Interior Minister Suleyman Soylu declared, “We are not only just Turkey, but also Damascus, Aleppo, Kirkuk, Jerusalem, Palestine, Mecca and Medina.”

Former U.S. officials involved in counterterrorism campaigns in the region say they have seen Turkish government maps showing their spheres of influence extending to into Saudi Arabia and down to Basra, Iraq.

Turkey’s longstanding rivalry with Saudi Arabia, which dates to the early 19th century, has erupted again, and was on full display during thediplomatic crisis over the murder of journalist Jamal Khashoggi by Saudi agents at the Saudi consulate in Istanbul on Oct. 2, 2018.

In the ensuing uproar, Turkey was careful not to rupture all ties with Riyadh. But its government did everything it could to embarrass and weaken Saudi Crown Prince Mohammed bin Salman.

Turkish President Recep Tayyip Erdogan used the fracas to declare that “Turkey is the only country that can lead the Muslim world.” That’s a direct rejection of the implicit claim of Saudi Arabia and the explicit claim of Iran to global Islamic leadership.

Annual conferences in Turkey bring together Erdogan’s AKP party with Arab Muslim Brothers from around the region to promote a Turkish-ledSunni Islamist political agenda.

Israel and Arab countries like Saudi Arabia, the UAE and Egypt are alarmed that they not only have to deal with expanding Iranian influence, but now face a Sunni Islamist alliance led by Turkey and financed by Qatar.

And they fear that if this coalition thrives, it could grow to include currently pro-American states such as Jordan and Kuwait.

The administration of President Donald Trump has been slow to react. Despite warnings from the diplomatic and security experts who formerly worked for Trump, there’s no sign that key U.S. leaders, including National Security Adviser John Bolton and Secretary of State Mike Pompeo, have figured out how to respond.

Now that Turkey is no longer a U.S. partner in the Middle East and has an agenda that clashes with the interests of the U.S. and its Israeli and Arab allies, changes in U.S. attitudes are required. That involves developing alternatives to the Incirlik Air Base in southern Turkey and cutting back on military cooperation and supplies, especially given Turkey’s provocative determination to purchase Russian S-400 anti-aircraft missiles.

The U.S. must be clear about its own expectations and leverage the cooperation that Turkey still needs to ensure that Erdogan respects the interests of the U.S.-led Middle East partnership.