The United States and Russia announced a plan for a “cessation of hostiles” in Syria that would initiate on Saturday, but it kept out groups such as the Islamic State and al-Nusra Front. This exclusion has already caught the eyes of  Syrian rebels, as they are considering it to be a serious loophole in the plan.

This agreement is described by a UN spokeswoman as “a first step towards a more durable ceasefire.”

The plan is the product of an intensive diplomacy between Washington and Russia, which back opposing sides in the 5-year-old civil war that has taken lives of more than 250,000 people, according to Reuters.

The Syrian army is supported by Moscow, Iran and Lebanon’s Hezbollah; combating against them are rebel forces backed by the US, Turkey and Saudi Arabia.

The settlement was discussed over phone by US President Barack Obama and Russian President Vladimir Putin. The leader of the Kremlin stated that the agreement could “radically transform the crisis situation in Syria.”

It permits the Syrian army, the allied forces and the Syrian opposition fighters, to react with “proportionate use of force” in self-defence, says News Corp.

The White House said that it could help advance talks on making a political change in Syria. The truce will need both the nations to convince their allies on the ground to conform.

Bashar al-Zoubi, chief of the political office of the Yarmouk Army, part of the Free Syrian Army, said that the agreement would envelop Syrian President Bashar al-Assad and his Russian allies, who would continue attacking opposition-held territory where rebel and militant factions are firmly crammed.

“Russia and the regime will target the areas of revolutionaries on the pretext of the Nusra Front’s presence, and you know how mixed those areas are, and if this happens, the truce will collapse,” he said.