Secretary of State John Kerry sent a strong warning to Syria, saying "the threat of force is real" if it does not carry out an internationally brokered agreement to hand over its chemical weapons.

Kerry issued the warning during a stop in Jerusalem, where he briefed jittery Israeli leaders on the new US-Russian plan to rid neighboring Syria of its chemical weapons by the middle of next year.

In comments aimed at his hosts, Kerry said the deal also served as a "marker" for the international community as it deals with Iran's suspect nuclear program. "We cannot have hollow words in the conduct of international affairs," Kerry said."These are crimes against humanity and they cannot be tolerated," Kerry warned.

The Syria deal was greeted with cautious optimism in Israel, where leaders expressed satisfaction that Syria, a bitter enemy, could be stripped of dangerous weapons but also pessimism about whether Syrian President Bashar al-Assad will comply.

Meanwhile, Syria's national reconciliation minister, Ali Haidar, hailed the US-Russia deal as a "victory" for his nation. "On the one hand they will help Syrians get out of the crisis, and on the other hand, they averted a war against Syria by removing the pretext for those who wanted to unleash one."