* Syrian opposition source says four-way talks set for Munich
* Russian diplomat says meeting not on Lavrov's agenda
* U.N. official says no plan for Brahimi to hold broad meeting (Adds comment from U.N. official and Russian diplomatic source)
MOSCOW, Feb 1 (Reuters) - Moscow and the United Nations played down reports that Syria's opposition leader would hold a joint meeting with the U.N. Syria envoy and officials from the United States and Russia at a security conference in Munich on Saturday.
Syrian opposition sources said on Friday that Syrian National Coalition President Moaz Alkhatib would meet Russian Foreign Minister Sergei Lavrov, U.S. Vice President Joe Biden and U.N. envoy Lakhdar Brahimi at a security conference in the German city.
But a U.N. official and a senior Russian diplomat said there no plans for them all to meet together.
"The U.N. special envoy is not involved in any trilateral meetings," a United Nations official said in Munich, adding that Brahimi planned separate meetings with Biden, Alkhatib and Lavrov.
Russian Deputy Foreign Minister Gennady Gatilov said Lavrov was not scheduled to take part in expanded talks.
"Media reports of a meeting in Munich in the format of Lavrov-Biden-Brahimi and Syrian opposition representative Alkhatib do not correspond with reality," he said. A Russian diplomatic source later said such a meeting could still come about "spontaneously", and that he did not rule it out.
Lavrov has yet to meet Alkhatib, who in December rejected a Russian invitation to come to Moscow for talks and urged Lavrov to apologise for what he said was Russian intervention in Syria and support for President Bashar al-Assad.
Alkhatib survived a challenge to his authority after saying he would be willing to talk to Syrian officials without President Bashar al-Assad stepping down first.
Russia, Syria's main arms supplier, has blocked three U.N. Security Council resolutions aimed at putting pressure on Assad. It says his exit from power must not be a precondition for a negotiated settlement of the 22-month-old conflict, which has killed more than 60,000 people. (Reporting by Gabriela Baczynska in Moscow and Myra Macdonald in Munich; Editing by Steve Gutterman and Kevin Liffey)