President Barack Obama's national security adviser, Thomas Donilon, has met Chinese President Hu Jintao to discuss security in the Middle East and Asia, AP reported. No details of their meeting Tuesday were immediately released, but the two were also expected to discuss bilateral relations, nonproliferation and global economic issues. Donilon's visit comes as Syria plunges deeper into violence with opposition fighters pressing their fight to topple President Bashar Assad. China joined Russia last week in vetoing a resolution backed by the U.S. and other Western nations that would have imposed new sanctions on Assad's regime. Donilon also met State Councilor Dai Bingguo, China's top diplomat.