MANILA (Reuters) -The Philippines and China agreed on Tuesday of the need to "restore trust" and "rebuild confidence" to better manage maritime disputes, even as Manila told its neighbour it will be "relentless" in protecting its interests in the South China Sea.

The Philippine foreign ministry said it had "frank and constructive" discussions with China on the South China Sea during the ninth round of talks under their Bilateral Consultation Mechanism, hosted by Manila.

The high-level meeting between senior foreign ministry officials followed what the Philippine military described as the "most aggressive" actions in recent history by China's Coast Guard against its vessels during last month's routine resupply mission that seriously injured a Filipino sailor.

"There was substantial progress on developing measures to manage the situation at sea, but significant differences remain," the Department of Foreign Affairs (DFA) said in a statement.

Earlier in the day, the Vatican's foreign minister Archbishop Paul Richard Gallagher, called for the peaceful resolution of conflicts, including in the South China Sea, which China mostly claims as its own territory.

"We encourage parties in conflict to abide by international law," Gallagher, who is in Manila for an official visit, said in a joint press briefing with his Philippine counterpart.

Manila has sought wider international support on its maritime claims, seeking closer ties with countries to advocate for a rules-based order that recognises international law.

The Permanent Court of Arbitration in 2016 said China's expansive claims had no legal basis.

But China, which maintained that its actions in the South China Sea have been lawful and professional, has said that it does not accept any claim or action based on the ruling.

"The Philippines will be relentless in protecting interests and upholding its sovereignty, sovereign rights and jurisdiction in the West Philippine Sea," the DFA said in the statement using the term Manila uses to refer to waters within its exclusive economic zone.

Manila and Beijing discussed their respective positions on the Second Thomas Shoal, where the Philippines maintains a rusting warship manned by a small crew, that it beached in 1999 to reinforce its sovereignty claims.

The two sides, the DFA said "affirmed their commitment to de-escalate tensions without prejudice to their respective positions."

"Both sides agreed to continue discussions to find mutually-acceptable resolution to the issues," the DFA said.

The Philippines and China have also agreed to explore a possible cooperation between their coast guards and a platform where scientists can collaborate.

(Reporting by Mikhail Flores and Karen LemaEditing by Ed Davies and Sharon Singleton)

By Mikhail Flores and Karen Lema