BEIRUT -- The embattled regime of Syrian President Bashar Assad promised Thursday to observe a U.N.-proposed truce during a four-day Muslim holiday, while rebels claimed major gains in the key battleground of Aleppo.

But prospects of the cease-fire taking hold are dim, given Assad's history of broken promises and the rebel momentum in Aleppo, Syria's largest city, where fighters said they advanced into several regime-held neighborhoods.

The truce plan by U.N.-Arab League envoy Lakhdar Brahimi has been endorsed by the U.N. Security Council, including Assad allies Russia and China. U.N. chief Ban Ki-moon urged all countries and groups with influence in Syria to pressure both sides to stop the violence in the civil war, his spokesman said.

The holiday cease-fire was the least a divided international community could agree on after the failure of a more ambitious plan for an open-ended truce and political transition talks by Brahimi's predecessor, Kofi Annan, in April.

Even the current truce, to begin Friday with the start of the Eid al-Adha holiday, appears in jeopardy from the outset. Neither side has shown an interest in laying down arms, instead pushing for incremental military gains.

Associated Press