NEW YORK, Dhu-AlHijjah 23, 1437, Sep 24, 2016, SPA -- The planned U.S. deployment of the THAAD anti-missile system in South Korea is not negotiable as part of efforts to agree new U.N. sanctions on North Korea after its fifth nuclear test, but Washington is confident tougher steps will be agreed before long, the senior U.S. diplomat for Asia said on Friday, Reuters reported. China, whose full backing is widely seen as crucial for sanctions on North Korea to be effective, is strongly opposed to the deployment of the Terminal High Altitude Area Defense system and some experts have argued it should be part of talks on new U.N. measures. But asked whether THAAD was negotiable, Daniel Russel, the U.S. assistant secretary of state for East Asia, referred to a U.S.-South Korean agreement on the deployment. "No. The two countries have made a decision," he told Reuters. Discussions are under way on a possible new U.N. sanctions resolution on North Korea after it conducted its fifth and largest nuclear test on Sept. 9. Russel later told a news briefing discussions were still at an early stage, but he was confident that a new U.N. resolution would be agreed before long, imposing further sanctions and tightening existing ones. Of the aims would be to prevent North Korea's abuse of international infrastructure, he said, including banking and shipping, to further its nuclear program. China is North Korea's main ally, but has been angered by its repeated missile and nuclear tests and backed tough U.N. sanctions on Pyongyang in March. -- SPA 01:42 LOCAL TIME 22:42 GMT www.spa.gov.sa/w