Ammon News - By Jay Solomon/ The Wall Street Journal

WASHINGTON—The U.S.'s closest Arab allies are jointly pressing President Barack Obama to take the lead in bridging the Middle East's divisions over Syria, traveling to Washington to personally drive home their fears that some of the region's other leaders are strengthening radicals and prolonging President Bashar al-Assad's rule.

The coordinated message was delivered to Mr. Obama during separate White House meetings in recent weeks with Jordan's King Abdullah II, the United Arab Emirates' Crown Prince Mohammed bin Zayed al-Nahyan and Saudi Arabia's Foreign Minister Saud al-Faisal, according to senior U.S. and Arab officials familiar with the discussions.

The three royals' message to Mr. Obama was a not-so-subtle slap at Qatar and Turkey—both of which, officials in these Arab countries believe, are funneling funds and possibly weapons to groups promoting political Islam and in particular to those aligned with the Muslim Brotherhood.

They are also concerned that aid from Qatar has bolstered the Al-Nusra Front, a powerful Syrian militia fighting Mr. Assad's forces, which the U.S. has designated as a terrorist organization.

"We need someone to manage the players" in the region, said a senior Arab official involved in the discussions. "The U.S. and the president are the only ones who can put Qatar in its place."

Qatari officials, who have publicly denied supporting the Al-Nusra Front, declined to comment Thursday. A Turkish official denied Prime Minister Recep Tayyip Erdogan's government was favoring Islamist parties in Syria or anywhere else in the region. "We just support the rights of the Syrian people," the official said.

Throughout Syria's conflict, the five Sunni lands have backed efforts to support the rebels. But they have largely broken into two camps when it comes to supporting specific rebel groups or leaders—which U.S., European and Arab leaders say has contributed to the fracturing of the opposition, both militarily and politically.

Saudi Arabia, Jordan and the U.A.E. are central players in American efforts to bring about an end to the civil war in Syria, contain Iran's nuclear program and kick-start a new round of Arab-Israeli peace talks. But the U.S. also relies heavily on Qatar and Turkey to advance a Syrian political transition and to restart the Mideast peace process.

Riyadh, Amman and Abu Dhabi are positioning themselves as a moderate front in the Syrian crisis, said these officials, seeking to support rebel factions not aligned with the Islamist Muslim Brotherhood or linked to extremist militant groups like al Qaeda.

Arab officials said they haven't pressed Mr. Obama to deploy American troops in Syria or to use U.S. warplanes. Instead, they hope he will play a higher-profile role in seeking to forge a moderate, unified coalition that is purged of "radical" elements that threaten Syrian minorities who might otherwise already have broken with Mr. Assad.

A White House official declined to comment on the specifics of Mr. Obama's talks with the three Arab leaders but stressed that he is aggressively working to unify the Mideast states on Syria.

Mr. Obama also met with Qatar's prime minister, Sheikh Hamad bin Jassim al-Thani, last month in Washington. He will host Mr. Erdogan at the White House in the coming weeks, the official said.

Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov announced on Tuesday a plan to host a new international conference on Syria, possibly by month-end in Geneva.

"A major part of the discussions has been and will continue to be what we can do together to support the Syrian opposition and bring an end to the bloodshed," said National Security Council spokeswoman Caitlin Hayden.

In more than two years since political rebellions broke out across the region, Jordan, the U.A.E. and Saudi Arabia have all been alarmed by the sudden dominance of the Muslim Brotherhood in the newly democratic governments in Egypt and Tunisia, viewing their emergence and ideology as threats to the stability of their monarchies.

Syria's civil war has posed a particular challenge to King Abdullah and the Hashemite Kingdom, which shares a long land border with Syria.

More than a half-million Syrian refugees have fled into Jordan over the past 18 months, placing strains on Amman's finances and public services, according to Jordanian officials. The influx also risks upending the country's fragile mix of Bedouin tribes, Palestinian refugees and political supporters of the Muslim Brotherhood, who have increasingly challenged King Abdullah's writ in recent years.

Qatar and Turkey, however, have both aggressively sought to use the Mideast's transition to expand their diplomatic, economic and religious influence, say U.S. and Arab officials.

The two countries have been the most aggressive in seeking to overthrow Mr. Assad. Qatar has been the primary financial supporter of the new governments in Cairo and Tunis, providing billions of dollars in aid to President Mohammed Morsi's government over the past 18 months, according to Qatari officials.

"In my opinion, some of our region, they did not like what happened…and they don't like it when the Muslim Brotherhood came," Sheikh Hamad, Qatar's prime minister, said in remarks in Washington last month. "But we respect the [other's] will and the people's will in the other nations."

Relations between the Obama administration and Jordan, Saudi Arabia and the U.A.E. have been strained by these seismic shifts in the Mideast's politics over the past two years, said U.S. and Arab officials.

Saudi Arabia and the U.A.E., in particular, believed the White House didn't do enough to support former Egyptian strongman Hosni Mubarak or Bahrain's royal family, said these officials.

The countries also felt the White House was naive to how Islamist organizations like the Muslim Brotherhood and Iran would seek to benefit from the region's political vacuums.

Still, the leaders from these countries have stressed in recent weeks that Washington is the only country that can prevent Syria from deteriorating into a failed state. Many worry this breakup could lead to zones of influence inside Syria, controlled by al Qaeda, the Muslim Brotherhood, and Iran and its allies.

"[There] has to be a transitional period that results in a political solution that includes all the segments of Syrian society, no exclusion whatsoever," Jordan's foreign minister, Nasser Judeh, said Wednesday in Rome, underscoring Amman's concerns about Syria's territorial integrity.

Mr. Obama's ability to unify the Arab states and Turkey will also be crucial for his attempts to revive the Arab-Israeli peace process.

Mr. Kerry has been shuttling between Mideast capitals since taking over the State Department in February in the hopes of reviving a 2002 Arab League peace initiative. It calls for Muslim countries to recognize Israel in return for the establishment of a Palestinian state based on the borders before the 1967 Arab-Israel war.

But power inside the Arab League and broader Muslim world has shifted dramatically since 2011, said American and Arab diplomats.

Egypt and Jordan had previously been the principal Arab supporters of the Palestinian diplomats, but Cairo and Amman are increasingly being replaced by Qatar and Turkey. Both countries have strong relationships with the Palestinian militant group Hamas, which has so far refused to recognize Israel as part of any peace negotiations.

Qatar's Sheikh Hamad currently heads the Arab League diplomatic team working with Mr. Kerry to restart the peace process. But some Arab officials said they are wary of his leadership and ties to Hamas. The Gulf kingdom currently hosts Hamas's political leader, Khaled Meshaal.