The United States has announced a suspension of its cooperation with Russia on the question of monitoring the truce in Syria, and stressed that it was not an easy decision.

"The United States is suspending its participation in bilateral channels with Russia that were established to sustain the Cessation of Hostilities. This is not a decision that was taken lightly," a spokesman for the U.S. Department of State, John Kirby, said in a statement on Monday.

At the same time, "to ensure the safety of our respective military personnel and enable the fight against Daesh [Islamic State, a terrorist organization banned in Russia], the United States will continue to utilize the channel of communications established with Russia to de-conflict counterterrorism operations in Syria," the spokesperson said.

The U.S. will recall its staff sent earlier to Geneva, which was awaiting the opening of the Joint Implementation Center, Kirby said.

"Unfortunately, Russia failed to live up to its own commitments - including its obligations under international humanitarian law and UNSCR 2254 - and was also either unwilling or unable to ensure Syrian regime adherence to the arrangements to which Moscow agreed," the spokesperson said.

"The United States spared no effort in negotiating and attempting to implement an arrangement with Russia aimed at reducing violence, providing unhindered humanitarian access, and degrading terrorist organizations operating in Syria, including Daesh and al Qaeda in Syria," the diplomat said.

"Russia and the Syrian regime have chosen to pursue a military course, inconsistent with the Cessation of Hostilities, as demonstrated by their intensified attacks against civilian areas, targeting of critical infrastructure such as hospitals, and preventing humanitarian aid from reaching civilians in need, including through the September 19 attack on a humanitarian aid convoy," Kirby said.