The Philippines is ready to help the US as it aligns its defences against threatened attacks by North Korea, the foreign minister said, hinting at the possibility of opening more Philippine bases to the US military.

U.S. forces have previously used military bases and civilian airports in the Philippines to repair and refuel aircraft and warships deployed in wars in Iraq and Afghanistan.

The U.S. has ships in Subic, the former home of the U.S. 7th Fleet, and aircraft at the nearby Clark airfield, another former U.S. base on the main island of Luzon.

"I think as treaty allies, if there is an attack, we should help one another, which is what the treaty alliance is all about," Foreign Affairs Secretary Albert del Rosario told journalists at a main army base in Manila on Friday.

Manila signed a Mutual Defence Treaty with Washington in 1951, one of the key links in the chain of security alliances the United States has with Asia-Pacific states, including Japan, South Korea, Singapore, Thailand and Australia.

On Friday the two countries began a fortnight of scheduled joint military exercises known as Balikatan ('shoulder to shoulder') which come amid high tensions on the Korean peninsula and in the South China Sea, where the Philippines is embroiled in a long territorial dispute with China.

"Balikatan with its complex and comprehensive set of exercises is an important contribution not only in preparing both our armed forces to work together but also in building my country's own capacity to defend itself," del Rosario said.

About 8,000 American and Filipino soldiers are taking part in this year's exercises, staging mock battles and simulating disaster responses. Nearly a dozen Asian and Pacific states are also taking part in a drill that examines how to handle vessel collisions in a busy shipping lane such as the South China Sea. – Reuters