ABU DHABI, 22nd February 2016 (WAM) — The United States and Russia agreed Monday on a new cease-fire for Syria that will take effect Saturday, U.S. officials said, even as major questions over enforcing and responding to violations of the truce were left unresolved. Where in Syria the fighting must stop and where counterterrorism operations can continue also must be addressed.

The new timeline for the hoped-for breakthrough comes after the two former Cold War foes, which are backing opposing sides in Syria’s civil war, agreed on terms for the “cessation of hostilities” between Bashar Assad regime and armed opposition groups, the officials told the AP. Those sides must accept the deal by Friday.

The truce will not cover ISIL, the al-Qaida-linked Nusra Front and any other militias designated as terrorist organisations by the U.N. Security Council. Both the U.S. and Russia are still targeting those groups with airstrikes. An announcement is expected after presidents Barack Obama and Vladimir Putin speak by telephone Monday, according to the officials, who weren’t authorised to speak publicly on the matter ahead of time and demanded anonymity.

The Bashar al-Assad regime has killed hundreds of thousands of Syrian civilians and forced some 12 million civilians from their homes after peaceful protests began in early 2011. The UN puts the number of recorded deaths in Syria at just 250,000 but stopped updating the death toll in January 2014. The war also created Europe’s worst refugee crisis since World War II and allowed ISIL to carve out territory across Syria and neighboring Iraq. Independent of Russia, a U.S.-led coalition is carrying out a separate bombing campaigns in Syria, targeting IS militants.

The plan largely follows the blueprint set by Washington, Moscow and 15 other countries at a conference in Munich, Germany earlier this month. That agreement called for a truce by Feb. 19, a deadline that was missed.

Beyond the new cease-fire date, Monday’s agreement sets up a “communications hotline” and, if needed, a working group to promote and monitor the truce. Violations are to be addressed by the working group with an eye toward restoring compliance and cooling tensions. The deal also calls for “non-forcible means” to be exhausted before other means are pursued for punishing transgressors.

Any party can report violations to the working group being co-chaired by the U.S. and Russia.

The two countries also will share “pertinent information” about territory held by rebel groups accepting the truce.

The timing of the cease-fire is only days ahead of Moscow’s proposal earlier this month for it to start on 1st March.

Washington rejected that offer at the time, saying it wanted an “immediate cease-fire” and not one that would allow Syria and its Russian backer to make a last-ditch effort for territorial gains in the Arab country’s north and south.

While negotiations dragged, however, Russian airstrikes pummeled areas in and around Aleppo, Syria’s largest city helping Assad’s military on the ground.

Syria’s conflict started with violent government repression of largely peaceful protests five years ago, but quickly became a full-blown rebellion against Assad and a proxy battle between his Iran-backed government and the rebels.