MANILA - PXP Energy said Thursday its chairman, Manuel Pangilinan, had sent "feelers" to China National Offshore Oil Co for possible joint exploration in the South China Sea.

Pangilinan is "hopeful" that the Department of Energy would allow work to resume in the area covered by PXP Energy's service contract, the company told the stock exchange, clarifying a Philippine Star report.

Survey work can start as soon as the Philippines and China agree on a protocol for joint exploration, Pangilinan was quoted as saying in the report.

Negotiations between PXP Energy, then known as Philex Petroleum, and state-run CNOOC stalled after the government of then President Benigno Aquino III in 2013 contested the validity of Beijing's sea claims before a United Nations-backed tribunal.

The Hague-based Permanent Court of Arbitration ruled in favor of the Philippines in 2016, shortly after Aquino's successor, President Rodrigo Duterte assumed office.

Duterte refused to flaunt the ruling and instead sought closer diplomatic and economic ties between the Philippines and China.