MANILA- Malacañang maintained Thursday that the Philippines’ sovereignty is "non-negotiable" even as the country pursues friendly ties with China.

Manila is “kind” to Beijing in terms of diplomacy but would not hesitate to assert its sovereignty, Presidential Spokesperson Salvador Panelo told reporters.

“We are kind in the sense that we are courteous to them but with respect to sovereignty issue, ibang usapan na 'yon (that’s a different issue). We have to assert our sovereignty,” he said.

Asked whether the Philippines is open to a compromise with China over the presence of Beijing’s vessels in Manila’s waters, Panelo responded: “It’s non-negotiable.”

The Philippines has filed a “salvo” of diplomatic notes to China over the presence of Chinese vessels near Pag-asa Island in the West Philippine Sea, Foreign Affairs Chief Teodoro Locsin Jr. said last week.

BEFORE going to successful China visit I fired off salvo of diplomatic notes so I would not be accused of insincerity if, as suggested, I fired them off AFTER the visited wch is sioki. Instructed shot over massing of moving vessels because circling establishes nothing. https://t.co/2AQYhpPEcu

— Teddy Locsin Jr. (@teddyboylocsin) April 2, 2019

The presence of Chinese vessels in Philippine waters may be discussed when President Rodrigo Duterte flies to Beijing later this month for the second Belt and Road Forum for International Cooperation, according to Panelo.

The Philippine military earlier said it has monitored more than 600 Chinese ships near Pag-asa Island since January of this year.

Satellite images taken in 2018 and released earlier this year also showed that Chinese fishing vessels account for the largest number of ships operating in the Spratlys in the West Philippine Sea.

Panelo added that China “should tell us exactly why they are there and what are they doing there in the first place.”

If Chinese vessels continue to stay in Philippine territory, Panelo said it would be considered an "assault" to Philippine sovereignty.

• Palace: Chinese presence in West PH Sea an ‘assault’ to PH sovereignty