Russia, Iran and Turkey are close to agreement on composition of a Syrian constitutional committee that could pave the way for drafting a new charter followed by elections, diplomats said on Monday.The foreign ministers of the three nations, who support opposing sides in Syria's nearly eight-year war, meet for talks on Tuesday in Geneva, where they are expected to seek the United Nations' blessing for their joint proposal, they added.Staffan de Mistura, U.N. Special Envoy for Syria who steps down at year-end, has tried since January to clinch agreement on the identity of 150 members of a new constitutional committee to revitalize a dormant peace process.President Bashar al-Assad's government and the opposition fighting to topple him have each submitted a list of 50 names, but the three nations have haggled over the final 50 members from civil society and "independent" members, diplomats say."The three countries are coming with a proposal for the third list, which has been the heart of the problem," said one diplomat.Turkey and other nations would consider working with Assad if he won a democratic election, Turkish Foreign Minister Mevlut Cavusoglu said on Sunday, two days before coming to Geneva to meet Russian counterpart Sergei Lavrov and Iran's Javad Zarif.Turkey supports rebel fighters who control part of northwest Syria. A year ago, Turkish President Tayyip Erdogan described Assad as a terrorist and said it was impossible for Syrian peace efforts to continue with him.De Mistura said at the weekend the constitutional committee could be a starting point for political progress."It does touch, for instance, on presidential powers, it could and should be touching on how elections are done, on division of power, in other words a big issue," he said.De Mistura will be under "heavy pressure" to accept the trio's proposal to complete the make-up of the constitutional body, but may leave the decision to U.N. Secretary-General Antonio Guterres in New York later this week, the diplomats said."The last word is with us, with the U.N., not with any country, as good and as powerful as they may be," he said on Sunday.