United Nations Secretary-General Ban Ki-moon is calling for calm in Lebanon, at the brink of a political crisis Saturday following President Emile Lahoud's departure from office.

The Lebanese parliament failed once again to appoint a new head of state Friday. Mr. Lahoud ordered the army to take charge of the nation's security, then stepped down as head of state at midnight (2200 UTC), when his term expired.

The United States also is urging Lebanon's political factions to maintain calm and promote security for Lebanon's citizens.

Mr. Lahoud, who is pro-Syrian, said he authorized the army to maintain order because the danger exists for a state of emergency. However, a spokesman for Prime Minister Fuad Siniora says the government rejects Mr. Lahoud's order to the army.

Lebanese political leaders scheduled another presidential vote in parliament for November 30.

Friday's scheduled presidential vote in Beirut was postponed after rival parliamentary factions failed to reach a last-minute accord on a successor to Mr. Lahoud.

Parliament's presidential election has been postponed five times already, in an attempt to find a consensus choice as head of state acceptable to both Lebanon's pro-Western governing coalition and the pro-Syrian, Hezbollah-led opposition.

Druze leader Walid Jumblatt says he spoke with Parliament Speaker Nabih Berri about postponing Friday's parliamentary session in order to preserve peace between the rival factions. Jumblatt is a key member of the pro-Western coalition, and Berri is a leader of Lebanon's pro-Syrian, Hezbollah-led opposition.

Failure to elect a new president on time could leave two rival governments battling for control, similar to the situation near the end of Lebanon's 15-year civil war in 1990.