The Philippines hopes to reach an agreement with Japan "at the soonest possible time" on allowing the deployment of military forces on each other's soil, the Philippine defense secretary said on Monday.

The two close U.S. allies have agreed to negotiate a reciprocal access agreement (RAA) amid growing tensions in the region. Both countries have maritime territorial disputes with an increasingly assertive China.

"We look forward to this reciprocal access agreement between both our countries given the commitment of the Japanese government and the Philippine government to preserve the rules-based international order and international law," Defense Secretary Gilberto Teodoro told a press briefing.

Once an agreement is reached, it would have to be submitted to the Philippine Senate and Japanese legislature for ratification, Teodoro said.

Japanese Prime Minister Fumio Kishida, on a visit to the Philippines on the weekend, said his country, the Philippines and the United States were cooperating to "to protect the freedom" of the South China Sea.

Teodoro was speaking on the sidelines of a ceremony at a military base, north of the capital, which is one of nine bases the United States has been given access to under the Enhanced Defense Cooperation Agreement (EDCA).

The United States has said it would allocate $100 million for infrastructure improves at the sites.

"The United States is helping the Philippine government in hardening its defensive posture to include its assertion of its legitimate rights in the West Philippine Sea," Teodoro said, referring to an area where tension has been rising between the Philippines and China over an over-lapping territorial claim.

The Philippines was "not seeking conflict", Teodoro said.