AMMAN, Jordan (AP) -- Anxious to keep Syria's civil war from spiraling into even worse problems, President Barack Obama said Friday he worries about the country becoming a haven for extremists when -- not if -- President Bashar Assad is ousted from power.
Obama, standing side by side with Jordan's King Abdullah II, said the international community must work together to ensure there is a credible opposition ready to step into the breach.
"Something has been broken in Syria, and it's not going to be put back together perfectly immediately -- even after Assad leaves," Obama said. "But we can begin the process of moving it in a better direction, and having a cohesive opposition is critical to that."
He said Assad is sure to go but there is great uncertainty about what will happen after that.
"I am very concerned about Syria becoming an enclave for extremism," Obama said, adding that extremism thrives in chaos and failed states. He said the rest of the world has a huge stake in ensuring that a functioning Syria emerges.
"The outcome is Syria is not going to be ideal," he acknowledged, adding that strengthening a credible opposition was crucial to minimizing the difficulties.
Eager to resolve another source of tension in the region, the president earlier Friday helped broker a phone call between the Israeli and Turkish prime ministers that led to the restoration of normal diplomatic relations between the two countries.
Obama had come to Jordan from Israel, where Israeli Prime Minister Benjamin Netanyahu placed a call to Turkey's Recep Tayyip Erdogan to apologize for the deaths of nine Turkish activists in a 2010 Israeli naval raid on a Gaza-bound international flotilla.
"The timing was good for that conversation to take place," Obama said.
Obama, at a joint news conference with Abdullah, said his administration is working with Congress to provide Jordan with an additional $200 million in aid this year to cope with the massive influx of refugees streaming into the country from Syria.
Abdullah said the refugee population in his country has topped 460,000 and is likely to double by the end of the year -- the equivalent of 30 million refugees in the United States, he said.
Obama also said he would "keep on plugging away" in hopes of getting the Israelis and Palestinians to reach a peace agreement.
"The window of opportunity still exists, but it's getting more and more difficult," the president said. "The mistrust is building instead of ebbing."
On Iran, Obama reiterated that the U.S. is open to "every option that's available" to keep the country from developing a nuclear weapon.
He said it would be "extraordinarily dangerous" for the world if Iran does become nuclear capable, and he expressed his desire for using diplomatic means to halt Iran's nuclear aspirations. Iran insists its nuclear program is for peaceful purposes.
"My hope and expectation is that among a menu of options, the option that involves negotiations, discussions, compromise and resolution of the problem is the one that's exercised," Obama said. "But as president of the United States I would never take any option off the table."
Obama arrived in Jordan on Friday evening, the final stop on a four-day visit to the Middle East that included his first stop in Israel as president.
He began his visit to Amman with an apology.
"I apologize for the delay," Obama told Abdullah after arriving about an hour behind schedule. "We ended up having a dust storm."
The two leaders headed to dinner after their news conference. On Saturday, Obama planned several hours of sightseeing, including a tour of the fabled ancient city of Petra, before the return trip to Washington.
Before leaving Israel, Obama paid his respects to the nation's heroes and to victims of the Holocaust. He also solemnly reaffirmed the Jewish state's right to exist.
Accompanied by Netanyahu and President Shimon Peres, Obama laid wreaths at the graves of Theodor Herzl, the founder of modern Zionism who died in 1904 before realizing his dream of a Jewish homeland, and former Israeli Prime Minister Yitzhak Rabin, who was assassinated in 1995.
He also toured the Yad Vashem Holocaust memorial, declaring afterward that it illustrates the depravity to which man can sink but also serves as a reminder of the "righteous among the nations who refused to be bystanders."
Friday's stop at Herzl's grave, together with Thursday's visit to see the Dead Sea Scrolls, the ancient Hebrew texts, were symbolic stops for Obama that acknowledged a rationale for Israel's existence that rests with its historical ties to the region and with a vision that predated the Holocaust. Obama has been criticized in Israel for his 2009 Cairo speech in which he gave only the example of the Holocaust as a reason for justifying Israel's existence.
"Here on your ancient land, let it be said for all the world to hear," Obama said. "The state of Israel does not exist because of the Holocaust, but with the survival of a strong Jewish state of Israel, such a holocaust will never happen again."
Obama and Netanyahu met for two hours over lunch. An Israeli official said that they discussed Israel's security challenges and that, in addressing the peace process with Palestinians, Netanyahu stressed the importance of security. The officials spoke on the condition of anonymity under diplomatic protocol.
Obama also squeezed in a stop in Bethlehem in the West Bank to visit the Church of the Nativity.
He had been scheduled to take a helicopter to Bethlehem but had to change plans due to unusually high winds. The route gave Obama a clear look at Israel's separation barrier with the West Bank, which runs south of Jerusalem and is the subject of weekly protests by Palestinians.
About 300 Palestinians and international pilgrims gathered near the Nativity Church, awaiting Obama's arrival. But a knot of protesters along the route held up signs stating: "Gringo, return to your colony" and "US supports Israeli injustice."
At a nearby mosque, Mohammed Ayesh, a Muslim religious official in Bethlehem, issued a plea to Obama in a speech to worshippers: "America, where are your values? Where are the human rights? Isn't it time that you interfere to make it stop?"
Amid high security, Obama toured the church with Palestinian Authority President Mahmoud Abbas. They stopped at the Grotto of the Nativity, which is said to stand where Jesus Christ was born. About 20 children waving U.S. and Palestinian flags greeted Obama in a courtyard outside the sanctuary. He posed for photographs with Abbas and Bethlehem's mayor, Vera Baboun.
At Yad Vashem, Obama donned a skull cap and was accompanied by Rabbi Israel Meir Lau, a survivor of the Buchenwald Concentration camp who lost both parents in the Holocaust. Among his stops was Yad Vashem's Hall of Names, a circular chamber that contains original testimony documenting every Holocaust victim ever identified.
"Nothing could be more powerful," Obama said.
Associated Press writers Dalia Nammari in Bethlehem, West Bank, and Daniel Estrin in Jerusalem contributed to this report.