"The United States supports the Secretary-General of the United Nations and the Secretary-General of the League of Arab States in calling on all parties in Syria to cease all violence during Eid al-Adha," the State Department said.
"We urge the Syrian government to stop all military operations and call on opposition forces to follow suit," it said in a statement.
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Washington for months has demanded an end to the bloody conflict in Syria and said that Syrian President Bashar al-Assad should go.
The Eid al-Adha festival, which coincides with the yearly pilgrimage to Mecca, is one of the holiest periods on the Muslim calendar. It begins on October 26.
UN-Arab League envoy Lakhdar Brahimi arrived in Damascus in Friday as he bids to secure a ceasefire in the conflict, which erupted in March 2011.
Arab League chief Nabil al-Arabi and UN Secretary General Ban Ki-moon pleaded with combatants to heed Brahimi's call "for a ceasefire and a cessation of all violence in all its forms during the period of the Eid al-Adha."
They called on "all regional and international actors to support this appeal."
Such a truce should last a long time, they said, as it "could create the space to allow a peaceful political process that realizes the legitimate aspirations of the Syrian people for democracy, equality and justice."
The US State Department said the government in Damascus "should also permit full and immediate humanitarian access to districts that have been under siege and allow vital supplies to reach people in need."
