BRUSSELS, Nov 9, (APP/AFP) – US leadership is essential in facing up to new security challenges, NATO head Jens Stolten berg said on Wednesday as he congratulated Republican Donald Trump on a stunning US election victory. “We face a challenging new security environment, including hybrid warfare, cyber attacks, the threat of terrorism. US leadership is as important as ever,” Stolten berg said. “I look forward to working with President-elect Trump,” he added.