Indonesia should step up and play a greater leadership role in Southeast Asia's management of maritime disputes with China, a group of foreign policy experts and academics said in an open letter.

"We should not forget that an 'independent and active' foreign policy does not give Indonesia a free pass to watch a strategic turmoil unfolding in its environment from the sidelines," said the 19 signatories from institutions across Indonesia.

The academics were responding to an international tribunal's ruling this month rejecting China's claim to exclusive control of most of the South China Sea, which hosts more than $5 trillion in international trade each year. The Philippines, which brought the case against China, is pushing the 10-member Association of Southeast Asian Nations to take a firmer stance on the issue.