UN Secretary-General Ban Ki-moon on Wednesday congratulated U.S. President Barack Obama on his reelection. \"The secretary-general warmly congratulates President Barack Obama on his reelection as president of the United States,\" Ban said in a statement. Obama on Tuesday won a second term in the White House, scoring a clear victory over Republican challenger Mitt Romney in a tight race that focused on how to repair the ailing U.S. economy. Ban said he looks forward to continuing to work with Obama and his administration in the spirit of the enduring partnership between the United States and the United Nations. \"Many challenges lie ahead - from ending the bloodshed in Syria, to getting the Middle East peace process back on track, to promoting sustainable development and tackling the challenges posed by climate change. All will require strong multilateral cooperation,\" Ban said in the statement. Ban also noted that the UN would continue to count on the active engagement of the U.S. on critical global issues.