SOCHI, Russia — U.N. Secretary-General Ban Ki-moon said on Friday a proposed international conference on Syria should be held as soon as possible, but that no date had yet been agreed.

"We should not lose the momentum," Ban said of a U.S.-Russian proposal to bring the Syrian government and opposition representatives to a peace conference.

"There is a high expectation that this meeting should be held as soon as possible," he said after talks with Russian Foreign Minister Sergei Lavrov.

Lavrov agreed. "The sooner the better," Lavrov told the joint news conference with Ban, who was due to meet President Vladimir Putin later on Friday.

Lavrov reiterated Russia's view that Iran should be invited to the conference, which could complicate its organization because of potential opposition from the West.

Iran is a U.S. foe and the main regional ally of Syrian President Bashar al-Assad's government, which has also received crucial support from Russia during its more that two-year-old civil conflict that has killed at least 80,000 people.