The Philippines and US armed forces will hold joint exercises over the coming fortnight as the rift deepens with Beijing over the strategic, resource-rich South China Sea.

The announcement about the joint planned exercise came hours after a phone call between US Defense Secretary Lloyd Austin III and his Filipino counterpart Delfin Lorenzana.

Philippines President Rodrigo Duterte had expressed his concern to China’s ambassador about Chinese vessels massing in the disputed waters, while Vietnam too has called on Beijing to respect its maritime sovereignty.

ENERGY EXPLORED: SUBSCRIBE TO ACCELERATE

Gain valuable insight into the global oil and gas industry's energy transition from ACCELERATE, the free weekly newsletter from Upstream and Recharge. Sign up here today.

International eyes are again focused on the South China Sea, where the Philippines Foreign Ministry described a fleet of more than 200 Chinese vessels as a “swarming and threatening presence” that “creates an atmosphere of instability”.

“Secretaries Austin and Lorenzana discussed the situation in the South China Sea, and the recent massing of People’s Republic of China maritime militia vessels at Whitsun Reef,” a Pentagon statement said.

Secretary Austin reiterated the US’ commitment to maintaining a free and open Indo-Pacific, rooted in international law, including the United Nations Convention on the Law of the Sea.

He proposed several measures to deepen defence co-operation between the US and the Philippines, including through enhanced awareness of threats in the South China Sea, but did not elaborate.

China's Foreign Ministry spokesperson Wang Wenbin earlier this year said: “The US frequently sent vessels and aircraft to the South China Sea to flex its muscles. This is not conducive to peace and stability in the region.

“China will continue to take necessary measures to firmly defend national sovereignty and security and work together with regional countries to safeguard peace and stability in the South China Sea,” said Wang.

Sediment coring

Meanwhile, China has been searching for methane hydrate deposits in the South China Sea, according to state media.

Chinese scientists on board a marine research vessel used the Sea Bull II drilling system to obtain a 231-metre sediment core at a depth of 2060 metres, reported official news agency Xinhua.

It was unclear exactly where the drilling took place in the South China Sea, some 90% of which is claimed by the Beijing administration.

Despite the political rhetoric and growing concern from allies, including the US, over the alleged incursion of Chinese vessels into the Philippines exclusive economic zone within the South China Sea, Duterte said he remains committed to diplomatically resolving the dispute with Beijing.

"We will continue to resolve the issues on [Whitsun Reef] through diplomatic channels and through peaceful means," said a statement from Duterte read by his spokesperson Harry Roque.

China’s stance is that Whitsun Reef, known as the Julian Felipe Reef in the Philippines, is a fishing ground where its vessels were merely seeking shelter from bad weather.

“We have made clear China's position on this issue many times in recent days. It is perfectly normal and irreproachable for Chinese fishing vessels to fish in the waters and take shelter during rough sea conditions," said China Foreign Ministry spokesperson Zhao Lijian.

“In total disregard of the facts, the US side obstinately refers to the Chinese fishing boats as ‘militia vessels’ and repeatedly invokes the illegal and invalid South China Sea arbitration award in an attempt to deny China's sovereignty, rights and interests in the South China Sea.

"The situation in the South China Sea is generally stable and China maintains close communication with the Philippines on relevant issues. We note that President Duterte said a few days ago that the Philippines will continue to resolve relevant issues peacefully through diplomatic channels," said Zhao.

"China urges the US side to respect the efforts of regional countries to properly address differences and maintain stability in the South China Sea and refrain from trying to sow discords."

Ill intention

“Its ill intention is doomed to fail.”

China, the Philippines, Vietnam, Malaysia, Taiwan and Brunei lay claim to all or some parts of the South China Sea, which is believed to have significant oil and gas potential.

Self-governed Taiwan, which China claims as its own territory, last week threatened to shoot down Chinese drones spotted circling the Taipei-controlled Pratas Islands in the South China Sea.