WASHINGTON - US Secretary of State John Kerry said on Thursday it was essential that a Russia-US deal on eradicating Syria's chemical weapons arsenal be enforced and that the UN Security Council must act on it next week."The Security Council must be prepared to act next week," Kerry told reporters. "It is vital for the international community to stand up and speak out in the strongest possible terms about the importance of enforceable action to rid the world of Syria's chemical weapons."Envoys from the five big UN powers are meeting in New York before the UN General Assembly next week to discuss a plan to place Syrian chemical weapons under international control.Crisis in Syria - full JPost.com coverageKerry said there was little doubt that the Aug. 21 gas attack on civilians outside Damascus was the work of Assad's forces and not of the opposition.Russia, which holds veto power in the Security Council, has said there is no proof that Assad's forces were responsible and denounced findings of a UN report that confirmed that the nerve gas sarin was used in the attack."This fight about Syria's chemical weapons is not a game. It is real. It is important," Kerry added. Kerry also said that recent comments by Iranian President Hassan Rouhani, who said on Wednesday his government would never develop nuclear weapons, were positive, but cautioned that "everything needs to be put to the test."Russia and the United States brokered the deal last week to avoid possible US military strikes. Under the deal, Syrian President Bashar Assad would account for his chemical weapons within a week and see them destroyed by the middle of next year.