The comments, by Foreign Secretary Albert del Rosario, followed China's weekend statement denouncing the Philippines for putting it under pressure with an international arbitration case over disputed waters.
In a position paper, China argued against the jurisdiction of the Permanent Court of Arbitration at The Hague to take up a case filed by the Philippines last year that could have implications for China's claims over the South China Sea.
"It is about defending what is legitimately ours," Philippine Foreign Secretary Albert del Rosario told Reuters in a text message.
"It is about seeking not just any kind of resolution but a just and durable solution grounded on international law."
China claims almost the entire South China Sea, rejecting claims to parts of it from Vietnam, the Philippines, Taiwan, Malaysia and Brunei. It has a dispute with Japan over islands in the East China Sea.
China has long rejected arbitration, insisting it would resolve disputes bilaterally. The tribunal has given China until Dec. 15 to reply in the case.
In March, Del Rosario argued the arbitral tribunal "has jurisdiction over all of the claims made by the Philippines and that every claim is meritorious". The Philippines laid out its argument in a 4,000-page document, including more than 40 maps.
Del Rosario said China's rejection of the arbitration would speed the process and a decision may be issued in the first quarter of 2016.
A ruling in the Philippines' favour could undermine parts of China's claim to the sea, which critics say has an obscure basis under the U.N. Convention on the Law of the Sea, to which China is a signatory.