Secretary-General Ban Ki-moon is urging countries supporting opposing sides in the Syrian conflict to redouble efforts to agree on a list of opposition groups to be invited to talks with the government scheduled to start in just a week.

Ban's appeal came as the U.N. envoy for Syria, Staffan de Mistura, briefed the Security Council Monday on his efforts to get the talks started and the leaders of Russia and Qatar met in Moscow to try to narrow their differences on Syria.

U.N. deputy spokesman Farhan Haq said the U.N. is focusing on starting the talks on Jan. 25, but he said it can't send out invitations until the key countries agree on an opposition list. He hinted the talks could be delayed.