MANILA - President Rodrigo Duterte assumed the chairmanship of the Association of Southeast Asian Nations (ASEAN) because the regional bloc's leadership rotates among its members, diplomatic officials said.

The President has been congratulated by supporters on social media for assuming the leadership of the 10-nation bloc.

Under Article 31 of the ASEAN's charter, "the chairmanship of ASEAN shall rotate annually, based on the alphabetical order of the English names of member states."

"Holding the chairmanship is on a rotation basis so we know when our turn is," Department of Foreign Affairs spokesperson Charles Jose told ABS-CBN News in a text message.

READ: Philippines to host ASEAN Summit in 2017

But Jose clarified that the alphabetical rotation for the chairmanship of the 10-member bloc is sometimes disregarded under certain circumstances.

This year's host, Laos, asked Malaysia to host the 2015 summit, one year ahead of schedule, to give it more time to prepare, a senior Filipino diplomat told ABS-CBN News.

Aside from the main summit, which sometimes includes leaders of ASEAN partners like the United States and China, the host country also organizes meeting of ministers and other officials.

ASEAN 2017, which also marks the organization's 50th anniversary, will be Duterte's first time to host international leaders in the country. The venue has not been decided.