UNITED NATIONS, Feb. 24 — The challenge is formidable, but U.S. and British diplomats are confident they can wring the nine votes necessary to win approval of the new Iraq resolution circulated Monday on the Security Council. The assessment is backed by other diplomats, although all agree that France, the most outspoken opponent as of now, could still use its veto power to kill the measure. UNDER THE U.N. charter, a resolution requires nine “yes” votes among the 15 Security Council members, and cannot be vetoed by the five permanent council members — Britain, China, France, Russia and the United...