If asked which Muslim country in the Middle East is most significant to them, many Americans might cite Saudi Arabia because of its oil.

Some might suggest Egypt because it is the heart of the Arab world. But the fact is that Turkey, perhaps with memories of past Ottoman glory, seems intent on becoming the most influential leader in the greater Middle East, and might overtake Saudi Arabia and Egypt in significance regionally, and for the United States.

Some have surmised that Turkey, a Muslim but non-Arab country with an image as “Islam lite,” could become a constructive counter to extremist Islamists in the area. In particular, it could be a counterforce to Iran, which already aspires to regional dominance. Thus Turkey would join Indonesia, another large Muslim but non-Arab country, as an example of impressive moderate Islamic statehood.

Though Turkey in the past has looked toward the West, it has in recent years been expanding its contacts and influence eastward into the Middle East. Amid the upheaval of the Arab Spring, its prime minister, Recep Tayyip Erdogan, has been mostly well received as a champion of democracy in countries now free, while strongly decrying the brutality under way in Syria.

But with Iran he has maintained a balancing relationship, on the one hand trying to protect it from tougher Western sanctions, but simultaneously approving installation in Turkey of a NATO missile shield clearly directed at Iran.

What also seemed to position Turkey as a potential problem solver in one of the region’s most intractable disputes, namely Palestinian statehood, was a friendly association with Israel, including diplomatic relations rare between a Jewish and an Islamic state.

But in recent months, that relationship has become badly frayed. Turkey has expelled Israel’s ambassador. Hopes that Turkey might be a useful interlocutor between the Israeli and Palestinian camps now seem remote.

Turkey is in a nasty diplomatic fight with the Jewish state, citing an agenda of complaints that conceivably could lead to a naval confrontation. Turks have sought to breach an Israeli maritime blockade of Palestinian Gaza, and Ankara threatens to use warships to assure free passage of aid to the coastal strip.

All this could not have come at a less opportune time for the US president.

He is in the midst of a reelection campaign in which the support and financing by American Jewry is important. His refusal to support the Palestinians’ bid for a vote on statehood at the United Nations, and his sturdy support of Israel throughout the UN bid, further erode his standing in the Islamic world.

It was in Turkey – and Cairo – early in his presidency that he delivered hallmark outreach speeches to the Islamic world. The criticism since from Arab capitals is that there has been no real follow-up. Now, having opposed the Palestinians’ UN request to recognize statehood, and being committed to the championship of Israel for an electioneering year, his popularity in Arab capitals is unlikely to improve.

President Obama clearly understands the potential importance of Turkey and its 77 million people. Of the few world leaders Mr. Obama scheduled for meetings alongside this year’s UN General Assembly session in New York, Mr. Erdogan was one. He got a long and earnest Obama appeal to cool the confrontation with Israel.

But Turkey can be independent. It resisted then-President George W. Bush’s entreaties to let American troops transit Turkish territory in 2003 to open a second front in the Iraq war. It may not be easily persuaded by Obama to abandon a tough line with Israel that plays well throughout the Arab world.

That is unfortunate. Erdogan is to be mostly commended for promoting his country’s blend of Islam with democracy as an example to be followed by Arab states emerging from dictatorship.

But it would be sad – and potentially harmful – if Turkey’s anti-Israel posture eliminated it from a constructive role in forging a peace deal between Israelis and Palestinians.