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.
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.