United Nations Secretary-General Ban Ki-moon is in Russia, where he said it is important to not "lose momentum" in setting up a peace conference on Syria next month.
Ban told reporters Friday that momentum gained by talks between U.S. Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov should be built upon, not wasted. He said a U.N. team is ready at any time to investigate claims that the Syrian government used chemical weapons against rebels.
Lavrov has said the sooner an international peace conference on Syria is held, the better. He also called on Syria to let chemical weapons inspectors into the country.
France's Foreign Ministry said Friday it opposes Iranian participation in the Syrian peace talks. A spokesman says France cannot see how a country that threatens regional stability like Iran can take part.
Lavrov has said Iran, a close Syrian ally, must be included in the talks. He accuses the United States and the West of trying to narrow the circle of participants.
This citizen journalism image provided by ENN shows black smoke rising from what rebels say is a helicopter that was shot down at Abu Dhour military airbase, Idlib, Syria, May 17, 2013.
A Free Syrian Army member prays next to the grave of a fellow fighter in a cemetery in Deir el-Zor, May 16, 2013.
Free Syrian Army members sit in a room inside a house in Deir el-Zor, May 16, 2013.
Crews demolish one of the damaged buildings at the site of the May 11 blast, in Reyhanli, Hatay province, May 15, 2013.
Members of the Free Syrian Army help a wounded fellow fighter in Deir al-Zor, May 14, 2013.
This image provided by Aleppo Media Center AMC shows the mother of a Syrian rebel cleaning a rifle, in Aleppo, May 14, 2013.
Syrians wait to cross back into Syria at the Turkish Cilvegozu border crossing in Reyhanli, Hatay province, May 14, 2013.
A view of the damaged Khalid ibn al Walid Mosque in Homs, Syria, May 14, 2013.
Syrian army soldiers inspect a house as they advance in on the village of Western Dumayna, near the rebel held city of Qusayr, May 13, 2013.
This citizen journalism image provided by Aleppo Media Center shows the famed 12th century Umayyad mosque in Aleppo, which was damaged by shelling, May 13, 2013.
The United States has not yet said who can attend, saying it does not want to make any pre-determinations.
The New York Times
reported Friday that Russia has sent more advanced anti-ship cruise missiles to Syria. At the same time, Russia says it has no interest in seeing Syrian President Bashar al- Assad remain in power.