The United States will transfer an observation blimp to the Philippines to help it track maritime activity and guard its borders amid rising tensions in the South China Sea, a U.S. diplomat said Monday.

Philip Goldberg, U.S. ambassador to the Philippines, said Washington would give Manila, its oldest Asia-Pacific security ally, $42 million worth of sensors, radar and communications equipment.

"We will add to its capability to put sensors on ships and put an aerostat blimp in the air to see into the maritime space," Goldberg said in an interview with CNN Philippines.