Turkey’s prime minister arrived in Iran on Thursday for talks dominated by the violence engulfing Syria, while U.N. chief Ban Ki-moon presented an Arab League summit in Baghdad with a U.N.-endorsed plan for ending the fighting and Secretary of State Hillary Rodham Clinton headed to the region for discussions focused on the crisis.

The Turkish leader, Recep Tayyip Erdogan, met with Iran’s parliamentary speaker, Ali Larijani, in Tehran and discussed ways “to help resolve complicated problems in the region,” Iranian state media reported.

Iran is optimistic about the six-point peace plan put forward by Kofi Annan, the joint U.N.-Arab League envoy to Syria, Iranian Foreign Minister Ali Akbar Salehi told journalists in Tehran. The plan has been endorsed by Syrian officials, although its call for an end to hostilities has not been implemented. On Thursday, Syrian media quoted President Bashar al-Assad as saying that he would “spare no effort to make this mission successful, since it is hoped that it will contribute to the return of security and stability to the country.”

Turkey’s leaders have pressed Assad to step down, accusing him of leading a brutal crackdown against a year-long uprising. Iran, however, remains staunchly supportive of Assad.

Turkey and Iran, neighboring nations with strong trade ties, are not likely to let their differences squander years of work to build good relations, said Henri Barkey, a professor of international relations at Lehigh University. Their mutual desire to remain on good terms could mean that Turkey is one of the few nations with leverage to sway Iran’s position, he said.

“Turkey is very dependent on Iran for energy, and Iran depends on being able to export fuel to Turkey,” Barkey said. “If I were Assad, I would be worried. If the Turks were to convince the Iranians that Assad is done for, the Turks might say, ‘Look, let’s find an alternative solution that you can live with.’ 

The Syrian crisis also topped the Arab League’s agenda in Baghdad, where leaders gathered amid high security for a summit postponed from last year. Ban urged Syria — which was not represented at the summit because its membership in the league has been suspended — to comply with Annan’s call for an end to hostilities and a daily cease-fire to allow for delivery of humanitarian aid.

“The world is waiting for commitments to be translated into action,” Ban said, according to wire service reports.

Inside Syria, meanwhile, violence continued. The Britain-based Syrian Observatory for Human Rights reported that 23 civilians were killed across the country Thursday, including five in the Qalaat al-Madiq area, near the central city of Hama, the scene of fierce battles between security forces and armed protesters in the past week. In addition, the group said, nine armed rebels and 15 members of the Syrian army were killed, including two officers assassinated in the city of Aleppo. 

In London, Foreign Secretary William Hague announced Thursday evening that Britain would supply almost $800,000 worth of nonlethal aid to the opposition inside Syria, led by the influential, if fragmented, Syrian National Council.

President Obama indicated at a nuclear summit in South Korea this week that the United States also would be prepared to expand its support to the Syrian opposition in the form of communications technology and medical aid.

Further discussions of the plans are expected at a Friends of Syria meeting of opposition leaders and representatives of supportive countries in Istanbul on Sunday.

The gathering in Turkey is a follow-up to a meeting in Tunis last month of more than 70 nations and international organizations that made little progress toward agreement on how to assist the Syrian opposition. Some Persian Gulf countries, notably Saudi Arabia and Qatar, called for arms shipments to Syrian opposition fighters. But other Arab League members and U.S. and European officials expressed concerns about the opposition’s unity and aims and insisted that nonviolent efforts to pressure Assad should first be exhausted.

Those disagreements remain and are likely to be aired during Clinton’s visit this week to Saudi Arabia, where she will stop en route to Istanbul. Clinton’s Friday meeting with Saudi King Abdullah will probably focus on Syria, even as the secretary reaffirms ever-closer U.S. relations with the Saudis on counterterrorism and other issues.

The Saudis, who have given the Syrian opposition money to buy weapons, have circulated a proposal in recent days calling for the establishment of a “safe zone” on the Syrian side of the Turkish border where humanitarian and military aid for the rebels can be assembled and distributed and the armed opposition forces can be trained. Although they don’t dispute negative assessments of the opposition fighters, the Saudis have argued that efforts to aid, unify and train them would be far easier in one location.

The Saudi proposal has met with little support. “If you’re going to have safety zones inside Syria, that’s basically a military operation,” said a senior Obama administration official, speaking on the condition of anonymity. “If it involves neighboring countries, that’s for neighboring countries to talk about, not the gulf” states.

The U.S. position, going into the Istanbul meeting, is that more time is needed to test Assad’s compliance with the Annan plan and to gauge the effect of tightening sanctions on the Syrian regime.

The Saudis, the U.S. official said, “would love us to be able to stand up and say Bashar is leaving tomorrow. That’s not going to happen. . . . What we’re doing is increasing diplomatic pressure” on Assad, “working on humanitarian access and pushing the transition forward.”

The Istanbul conference, the official said, “is a way for us to publicly acknowledge that type of momentum.”

Turkey has also been reluctant to agree to any official use of its territory by Syrian opposition forces without an international mandate, ideally from the U.N. Security Council.

On Saturday, Clinton is to meet in Riyadh with the six-member Gulf Cooperation Council of Persian Gulf states. In addition to Syria, council members are anxious to discuss Iran. With the Tehran government and the P5-plus-1 nations — the United States, Russia, China, Britain, France and Germany — agreeing to hold talks on the Iranian nuclear program, “we want to hear some kind of statement” about U.S. policy, a senior diplomat from the region said.

“If the talks succeed, what happens? If they fail, what happens? the diplomat said.

“We keep hearing that the United States will not allow Iran to get a nuclear weapon and that the United States is committed to Israel’s defense and nonproliferation,” the diplomat said. “We hear all the great reasons why the United States is going to work very hard to prevent this, but we don’t seem to be part of the messaging. . . . We want to hear what the plan is.”

DeYoung reported from Washington.