DOHA, Qatar — Syrian opposition factions signed a tentative agreement on Sunday to create an umbrella organization, paving the way for international diplomatic recognition as well as more funding and improved military aid from foreign capitals.

After three days of haggling at a luxury hotel here, opposition negotiators agreed to the new coalition and then elected as its president Sheikh Ahmad Moaz al-Khatib, a former imam of the historic Umayyad mosque in Damascus and a respected national figure within Syria. “Today in Doha is the first time the different factions of the Syrian opposition are united in one body,” said Riyad Farid Hijab, a former Syrian prime minister and the highest-level defector from the Damascus government. “So we ask the international community to recognize the Syrian opposition as the representative of the Syrians.”

The umbrella organization was designed to subsume the Syrian National Council, a previous attempt at unification that has appeared increasingly marginalized as Syria has descended into civil war. That group’s authority was undercut when it failed to attract sufficient support from key minorities, religious and tribal figures, businessmen, and, most important, rebel units conducting the fighting against President Bashar al-Assad’s forces.

The hope among Western countries is that the new coalition, called the National Coalition of Syrian Revolutionary and Opposition Forces, can give local opposition councils the legitimacy to bring fighters under their authority. That would give an important countervoice to the well-armed jihadist commanders who in many places have set the pace of the fighting and created worries that Islamists will gain a permanent hold.