The United States, Russia, Saudi Arabia and Turkey put forward new ideas Friday to revive a failed push for a political transition in Syria that could end the country's civil war, US Secretary of State John Kerry said Friday. But they remained deeply divided over the future of Syrian President Bashar al-Assad.

The top diplomats from the four countries agreed to meet again in an expanded format with representatives from other nations next week, but the only concrete result of this week's talks appeared to be an agreement between Jordan and Russia to coordinate military operations in Syria. Kerry said there was no decision on whether to invite Iran, a major patron of Syria.

Kerry said that he, Russian Foreign Minister Sergey Lavrov, Saudi Foreign Minister Adel al-Jubeir and Turkish Foreign Minister Feridun Sinirlioglu went over proposals to restart moribund talks on how to create a transitional government for Syria.

After the meeting, Kerry told reporters the "meeting was constructive and productive and succeeded in surfacing some ideas, which I am not going to share today, but which I hope have a possibility of changing the dynamic."

Lavrov said he has invited the US, Saudi Arabia and Turkey to join a coordination center that Russia and Jordan agreed earlier Friday would be used to integrate their air campaigns over Syria. Jordan is a member of the US-led coalition bombing Islamic State facilities in Iraq and Syria. The coalition has so far refused to cooperate with Russia's operations beyond a basic agreement intended to prevent mid-air incidents. Mohammad al-Momani, Jordanian government spokesman said the agreement did not mean that Jordan was leaving the coalition.

Kerry, who is travelling to Jordan later Friday for talks with King Abdullah II and Palestinian leader Mahmoud Abbas, said the new ideas "are in keeping with all of the principles that have been laid down and with sensitivities of the nations and the parties, the opposition, all those involved in this effort." He said Friday's participants would meet again as early as next Friday.

A leading Syrian opposition group, the Syrian National Council, said it still aimed for Assad's ouster. "We will not accept the presence of Assad for one day in the transitional period," said Anas al-Abdah, a member of the coalition, in a statement emailed to AP.

The US, Turkey and Saudi Arabia all share the view that Assad must go if the conflict is to be resolved. Russia began airstrikes in Syria last month that it said were aimed at Islamic State militants, but the US and its allies say the bombing is bolstering Assad rather than targeting militants.

Kerry said that the US and allied nations "understand that Assad creates an impossible dynamic for peace." Kerry suggested political talks could patch up the differences.

Lavrov said Russia's support for Assad remains strong. "Our partners have some obsession with the figure of the Syrian president, but we reaffirmed our position," Lavrov said.

One item on the agenda, Kerry said, is which nations should be included political transition discussions. Russia is keen to bring Iran into the talks, but Saudi Arabia is opposed. The Obama administration has said repeatedly that all the countries with an interest in Syria, including Iran and Russia, need to agree on a unified, secular and pluralistic Syria governed with the consent of its people.

Syria is in its fifth year of a civil war that has killed hundreds of thousands, spurred a massive refugee crisis in Europe and led to the emergence of the Islamic State group and Russia's direct military intervention.

Friday's meetings in Vienna followed a surprise visit by al-Assad on Tuesday to Moscow. There, he and Putin discussed Russia's military operations in Syria.