American policy may have compelled the Arabs and Turks to set aside their differences in Syria.

Qatar, Saudi Arabia and Turkey appear to have mended a rift that kept them from coordinating their efforts in support of the Syrian opposition.

The Washington Post reported last week that the three countries had ended a long estrangement to address their shared concern over the lagging fight against Syria’s president, Bashar al-Assad.

The initiative comes amid a growing sense in the region that the United States is preoccupied with its nuclear negotiations with Iran and the fight against the Islamic State in Iraq.

Turkish leader Recep Tayyip Erdoğan has publicly said that toppling Assad remains the priority for him. In an interview last year, he blamed the Syrian dictator for effectively creating the Islamic State insurgency which the United States now see as the greater threat in the Middle East.

Forces loyal to Assad, including fighters from the Lebanese militia Hezbollah, have mostly left the Sunni radicals of the Islamic State — who operate in both Iraq and Syria — alone while concentrating their firepower on less radical opposition groups. A Syrian military intelligence defector told Abu Dhabi’s The National newspaper that the regime had released “extremists” from detention while keeping political prisoners and protest leaders locked up.

From the start of the rebellion against him more than four years ago, Assad insisted his opponents were terrorists. He seems to have worked hard to make that characterization come true. In the meantime, tens of thousands of civilians are estimated to have died in the conflict.

While Jordan, Saudi Arabia and the United States supported relatively moderate opposition forces in Syria, initially with only nonlethal aid, Qatar and Turkey were less discriminate, backing Islamists as well whom they believed were more capable of defeating Assad.

For the Arabs, removing Assad would be a victory in their struggle for hegemony with Iran, the Syrian’s only ally.

Turkey interpreted the Syrian uprising as another front in the “Arab Spring,” a regional protest movement that was quickly hijacked in most places by Islamists and one that Turkey, keen on reclaiming its leadership in the Middle East, saw as an opportunity to expand its influence.

Qatar and Turkey betted specifically on the Muslim Brotherhood — and lost. The group was marginalized in Syria and defeated in Egypt where a Saudi-backed military coup removed the Islamists from power in 2013.

Saudi Arabia is apprehensive about the Muslim Brotherhood. The group’s brand of political Islam is at odds with the kingdom’s own puritanical strain of the religion, Wahhabism. The Muslim Brotherhood also favors republicanism and is populist. Saudi Arabia, by contrast, is a monarchy and authoritarian.

The Saudis previously allowed Qatar and Turkey a sphere of influence in the north of Syria while they concentrated their efforts on opposition groups in the south, near the Jordanian border.

Qatar and Turkey now seem willing to accept Saudi leadership in the campaign while the Muslim Brotherhood may be sufficiently weakened to no longer worry the kingdom.

Kyle W. Orton writes at The Eastern Project that Saudi Arabia has “called off its anti-Muslim Brotherhood campaign” while Erdoğan, in March, publicly agreed to work with the Saudis in Syria. The two still don’t see eye to eye when it comes to Egypt or Libya — where they support opposing sides in another civil war. “But a modus vivendi has been reached,” according to Orton.

The Washington Post reports that the influx of additional weapons and financial aid from Qatar, Saudi Arabia and Turkey has facilitated recent advances against the loyalists in Syria. Islamist groups, including those linked to the international terrorist organization Al Qaeda, are fighting with supposedly moderate rebels under a new umbrella group called the Army of Conquest.

Regional officials insist that the aid, including US-made TOW missiles, is not going to the Islamists. Instead, they said, it is enabling moderates to enhance their stature among opposition fighters after years of being outgunned and outfinanced by more militant groups.

Beyond exasperation in the region about the United States’ unwillingness to expand its own support for the Syrian opposition — for fear of inadvertently aiding fanatics that are also anti-American — the prospect of successful nuclear negotiations with Iran may have compelled the Arabs and Turks to set aside their differences.

America’s Middle East allies worry that it will acquiesce in Iran’s recent strategic gains in the Levant in order to get a long-term agreement to halt its nuclear program or even pursue broader rapprochement with a country that severed its ties with the West in 1979.

The Arab states and Iran also back opposing sides in Yemen where Saudi Arabia led a coalition of Sunni states to intervene in March on the side of the internationally-recognized government. Iran supports Yemen’s Houthi rebels who share its Shia faith.