"The United States is suspending its participation in bilateral channels with Russian Federation that were established to sustain the cessation of hostilities", John Kirby, the State Department spokesman, said in the statement, referring to the agreement on Syria reached with Russian Federation on September 9.
Zeid says that attacks over the last 10 days in rebel parts of Aleppo, including airstrikes by Syrian and Russian forces, have been "the most intense" there since Syria's civil war began in 2011.
The suspension in Syria talks was announced just hours after the Kremlin said Russian President Vladimir Putin had signed a decree halting a joint program with the US on the disposal of weapons grade plutonium.
In Moscow, Russian Foreign Ministry spokeswoman Maria Zakharova voiced regret about the USA move and blamed Washington for the failure to persuade the moderate Syrian rebels it backs to cut ties with extremist groups.
Further, the Secretary of State accused Russian Federation and Syria of being the only actors in the Syrian war who had yet to agree to the delivery of global aid into besieged areas of the country.
The spokesperson also accused Moscow and Damascus of targeting civilian areas and critical infrastructure such as hospitals and preventing humanitarian aid from reaching civilians in need.
Russian Federation does not shy away from its responsibilities on Syria, but the crisis can only be settled through joint efforts, including with the United States, Foreign Minister Sergey Lavrov added.
It could also trigger deeper USA consideration of military options such as providing more sophisticated arms, logistical support, and training to Syrian rebel groups that U.S. officials have said were under consideration, either directly or via Gulf Arab states or Turkey. Coupled with a Russian announcement to put on hold a plutonium disposal deal with the USA, it showed chilly relations between the former Cold War foes turning even frostier.
The U.S. had agreed to separate the rebel groups but noted it was an extremely slow process. Washington said the strike was launched by mistake, but Moscow has questioned the US explanation.
"I think everybody's patience with Russian Federation has run out", White House Press Secretary Josh Earnest said today during his daily press briefing.
China's U.N. Ambassador Liu Jieyi said now was the time for more cooperation, but Britain's Ambassador to the U.N. Matthew Rycroft said he was not surprised by Washington's action.
Syria's government and its allies had undertaken a "pattern of attacks" against targets with special protection under worldwide humanitarian law, including medical units, aid workers and water-pumping stations, he said.
Asked if the system posed a threat to US aircraft or crews, Cook said, "It depends on how the Russians plan to use it". When it was signed in 2000, the deal was touted as an example of successful cooperation between Washington and Moscow. But despite the timing, Elizabeth Trudeau, a State Department spokeswoman, said she does not see a link between the suspension of the plutonium deal and the Syrian talks.