This warning has come as an urgent call on the part of most of the rest of the world for the US to seriously assist in the defusing of tension in the Middle East. The threat of Israel's nuclear arsenal has destabilised the region for thirty years encouraging others to seek such an arsenal. Furthermore the US has been asked to use the same language with Israel that it uses with Iran, Hamas, Hesbollah in order to create the recognition that it is as it claims an honest broker in the region.
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from the article: U.S. warns Syria: Stop arming Hezbollah immediately