The UN chief says a shaky ceasefire in Syria is holding "by and large" on its third day, despite scattered fighting and growing accusations of violations.
However, a war of words between the Syrian government and Saudi Arabia, a key backer of the opposition, has added to rising tensions.
Speaking in Geneva, Ban Ki-moon, the UN secretary-general, confirmed receiving a letter from the High Negotiations Committee (HNC), the main umbrella opposition group, complaining of continuing violations by the Syrian government and its Russian and Iranian backers.
The letter, sent on Sunday, urged the UN to help "specify the territory covered by the truce to prevent hostilities."
Why not send in a United Nations peace keeping mission to enforce the cease fire? Ban Ki-moon from South Korea is the UN secretary-general why is he not more pro-active? According to the Charter, the UN has four purposes:
to maintain international peace and security;
to develop friendly relations among nations;
to cooperate in solving international problems and in promoting respect for human rights; and to be a centre for harmonizing the actions of nations.