"It's unhelpful to mutual understanding between China and the US. That is not conducive [to] the ongoing talks", he said.
Plus, the sea is a major global trade link - commodities from Africa and West Asia travel through South China Sea en route to China, Japan and South Korea.
During the briefing, Rep. Gary Alejano revealed that members of the Philippine Navy were being harassed by the Chinese Coast Guard in the West Philippine Sea.
"We're not asking you to trust us blindly. We've very open about them, and report them", he said. But we're in a democracy.
"I challenge anyone of them, whatever their profession - justice, politician, newsman, journalist - if we lost a single island during Duterte's time, I will pack my bags, go home". Called "Xisha" in Chinese, the islands have been incorporated into the southern province of Hainan and are being developed for tourism, as well as being equipped with weapon systems meant to enforce China's claim to virtually the entire South China Sea.
"China also assured us with our good relationship that we are not their enemy", he said.
"The president has said that".
Duterte's predecessor, Benigno Aquino III, questioned China's claims before a United Nations-backed arbitration court.
Critics, on the other hand, claim Duterte's "defeatist" approach has emboldened China, which has been increasingly assertive in the potential oil- and gas-rich waterway.
"We have strong evidence that China has deployed anti-ship missiles, surface-to-air missile (SAM) systems, and electronic jammers to contested features in the Spratly Islands region of the South China Sea".
The Pentagon last sent a US ship through the same waters in March, near Mischief Reef in the Spratly Islands. "This is merely set aside in the meantime, in line with the efforts of government at promoting peace, stability, and cordial relations among claimant countries in the region", Esperon said in a statement sent to media Wednesday.
National Security Adviser Hermogenes Esperon Jr. assures the public that the Philippine government is diplomatically finding its way around the issues in the West Philippine Sea.
He said lighthouses were being constructed on Philippine-occupied islets and the government has been improving port facilities and a partly eroded airstrip on Thitu island.
China says navy pilots aboard the country's sole operating aircraft carrier have completed their first nighttime takeoffs and landings.
On Sunday, two U.S. warships sailed close to islands occupied by China in the Paracel group, and last week the United States military withdrew China's invitation to take part in the upcoming Rim of the Pacific exercise in Hawaii "as an initial response to China's continued militarisation of the South China Sea".
The statement comes only days after recent news that two American naval vessels, the USS Higgins, a destroyer class ship, and the cruiser class USS Antietam, sailed within 12 nautical miles of the Paracel Island chain on May 27.
However, Cayetano said the president, who has been criticised for his refusal to confront China with the Philippines' 2016 victory at the Hague Tribunal, had warned that he would go to war with Beijing if it broke his "red lines" relating to the South China Sea. The operation that was conducted on Sunday had been undergoing drills and planning for months on end.
Previously in a speech in Davao City in February, he said: "This is not the time to be fighting over the South China Sea because it will only lead to war".
Esperon reported that five lighthouses have been built on Pag-asa, Likas, Parola, Patag and Kota islands - all part of the Kalayaan Group of Islands "to ensure safety of navigation, along our responsibility under the UNCLOS (United Nations Convention on the Law of the Sea) to provide navigational safety for all worldwide vessels transiting the West Philippine Sea".