Bahrain's king said Monday he is strongly in favour of a Saudi proposal to upgrade the Gulf Cooperation Council into a union.

"Bahrain is ready from this day for the declaration of the union, to assert our firm will and our solid determination," King Hamad said in an address on the occasion of the kingdom's national day.

"We look forward to the call for a special Summit in Riyadh to announce the establishment of this union," he added.

The six conservative Arab members of the GCC -- which includes Saudi Arabia, Bahrain, Kuwait, Qatar, the United Arab Emirates and Oman -- sit on 40 percent of the world's oil and a quarter of its natural gas.

The proposal to upgrade the bloc from a coordination council to a union was put forward by Saudi King Abdullah in 2011.

Bahrain's Sunni monarchy, which at the time was grappling with Arab Spring-inspired protests by its Shiite majority, strongly supported the proposal.

But other Gulf states have shown less enthusiasm, with Oman threatening last week to quit the loose alliance if the union proposal is pursued.

Divisions have surfaced within the bloc -- established in 1981 to put up a united front against Iran -- just as Tehran has managed to break its isolation, reaching a preliminary deal with world powers on its controversial nuclear programme.