A Senior U.S. military officials said on Friday that Russia has agreed to maintain hotline aimed at preventing mid-air collisions in Syria.

The so-called deconfliction line has been a lifesaving -- albeit imperfect -- tool since it was set up soon after Russia entered Syria's civil war in late 2015 to prop up regime leader Bashar al-Assad.

Even though the US military used the hotline to warn Russia of the impending missile strike on an Assad air base near Homs early Friday, a furious Moscow reacted to the attack on its ally by saying it would no longer cooperate with the Americans.

The hotline was established between US officers monitoring the war from an operations center at a base in Qatar, and their Russian counterparts operating in Syria.

The link is just a regular phone line staffed on the US side by a Russian-speaking colonel and has been used almost daily since its inception.