Leading political figures from both the U.S. and U.K. were pushing Saturday for a diplomatic solution to the civil war that has wracked Syria for the last four years. Both Britain's Prime Minister and U.S. Secretary of State John Kerry were reportedly lobbying for a diplomatic resolution to the crisis, on the sidelines of the United Nations' General Assembly in New York.

Kerry met with Iranian Foreign Minister Mohammad Javad Zarif on Saturday, and officials told the Reuters news agency that he hoped to launch a new diplomatic effort at the UN, where world leaders are meeting this weekend for the body's 70th annual general assembly.

"I view this week as a major opportunity for any number of countries to play an important role in trying to resolve some of the very difficult issues (of) the Middle East," Kerry told the Associated Press. "We need to achieve peace and a way forward in Syria, in Yemen ... in the region itself (and) I think there are opportunities this week, through these discussions, to make some progress."

The new U.S. approach, which officials stressed was still in its early stages, could bring Russia, a major supporter of Syria's Assad regime, together with countries such as Saudi Arabia, Turkey and that support Syrian opposition groups.

Meanwhile, British Prime Minister David Cameron is expected to call for a new initiative to secure peace in Syria, and to drop his opposition to Syria's Assad playing a role in any transitional government that might arise after the war. Cameron, along with U.S. leaders, had previously called for Assad to step down before any transitional government was formed, but officials told the BBC that such opposition would now be dropped, in favor of Assad stepping down at a later point.

In addition, U.N. Secretary-General Ban Ki-moon urged Iranian President Hassan Rouhani to "contribute to a political settlement of the crises in the region," and singled out both Syria and Yemen as countries that Iran could bring its influence to bear in resolving conflicts.