Secretary of State John Kerry is reopening the possibility of Iran playing a role in the Syrian peace talks, suggesting the entire Middle East region will remain unstable unless all countries come together at the negotiating table.

“Iran certainly does have an ability to be able to help make a difference,” Kerry said at the talks in Montreux, Switzerland. “There are plenty of ways that that door can be opened in the next weeks and months. And my hope is that they will want to join in a constructive solution.”

His remarks are the latest in a surprising turn of events that started earlier this month when Kerry suggested Iran could be part of the talks, triggering strong skepticism about the idea.

However, United Nations Secretary-General Ban Ki-moon on Sunday extended the invitation to Iran, only to rescind it a day later when Tehran rejected the principles of a 2012 peace plan that is the basis for the most recent negotiations.

Representatives for Syrian President Bashar al Assad and rebel forces are meeting, under U.N. supervision, to try to end their country’s roughly 3-year-long civil war in which 130,000 have been killed, included hundreds by chemical weapons allegedly deployed by the Assad regime.

Millions more have been forced from their homeland, creating an international refugee crisis.

Kerry has argued no peace accord can be reached until Assad is no longer in power -- ahead of the talks that got off to a rocky start Wednesday over Assad's future.

The international conference was organized to try to map out a transitional government and democratic election.

Russia, one of Syria’s other close allies, is attending the meetings, which also have been complicated by Assad's delegates and the Western-backed opposition Syrian National Coalition each claiming to speak for the Syrian people.

Kerry said that Saudi Arabia deciding to attend was crucial.

“I’ve just spent a month in the region, and everybody I spoke to said that there is simply no way that things will get better, whether in Syria or in the region, if you don’t get Iran and Saudi Arabia to talk to each other,” he said. “Saudi Arabia wasn’t going to be here, but they decided that it was important and they came.”

U.N. mediator Lakhdar Brahimi will meet separately with both Syrian sides on Thursday to see if they can even sit together in face-to-face talks due to begin Friday.

He said both sides had shown some willingness to bend on humanitarian access and local cease-fires, and he hoped to build on that common ground.

The U.S. and the Syrian opposition opened the conference by saying that Assad lost his legitimacy when he crushed the once-peaceful protest movement against his regime.

"We really need to deal with reality," Kerry said. "There is no way possible in the imagination that the man who has led the brutal response to his own people could regain the legitimacy to govern.”

The Syrian response was firm and blunt.

"There will be no transfer of power and President Bashar Assad is staying," Syrian Information Minister Omran al-Zoubi told reporters.

Syrian Foreign Minister Walid al-Moallem, who refused to give up the podium despite numerous requests from the U.N. chief, declared that terrorists and foreign meddling had ripped his country apart.

"You live in New York. I live in Syria," he angrily told Ban. "I have the right to give the Syrian version here in this forum. After three years of suffering, this is my right."

Ahmad al-Jarba of the Syrian National Coalition had wavered up to the last minute on whether to attend the peace talks that have been largely opposed by rebel brigades in Syria.

He said any discussion of Assad's continued hold on power would effectively end the talks. A transitional government "is the only topic for us," he said.

But al-Moallem insisted that no one except Syrians could remove Assad. He also accused the West and neighboring countries -- notably Saudi Arabia, which he did not name -- of funneling money, weapons and foreign fighters to the rebellion.

Al-Moallem also criticized the opposition coalition, which is based in Turkey and is largely made up of exiles with little sway on events inside Syria.

State Department spokeswoman Jen Psaki later criticized the Syrian government's rhetoric as "inflammatory."

“The fighting began with a peaceful uprising against Assad's rule in March 2011, according to activists, who are the only ones still keeping count after the U.N. abandoned its efforts.

Saudi Foreign Minister Saud al-Faisal, whose government has funneled millions to the rebels, said "it goes without saying that Assad has no role in Syria's future."

The Associated Press contributed to this report.