"It is inevitable that the Gulf Cooperation Council (GCC) states will have no choice but to improve their relations to an advanced form of a union," Ahmad al-Saadun said on his Twitter account.
This will make the member states "capable of confronting potential challenges targeting their interests, security and even their very existence," Saadun said.
But he insisted that all member countries of the proposed union must have similar regimes that are open to their people and respect human rights and freedoms.
This should include "freedom of expression and the right of popular participation in decision-making which we hope will be achieved in all GCC states shortly so the union can be established under its umbrella," the veteran opposition figure said.
The GCC consists of Bahrain and Kuwait, the only two states with elected parliaments, in addition to Saudi Arabia, the United Arab Emirates, Oman and Qatar, which have appointed or partially-elected assemblies.
Gulf leaders agreed on Monday to allow more time for further discussions over a Saudi proposal to turn the GCC into a union likely to start with the kingdom and unrest-hit Bahrain.
The union was first floated by Saudi King Abdullah in December. Bahrain’s state minister for information, Samira Rajab, said it could follow the "European Union model."
The GCC was formed in 1981 when the Sunni-dominated monarchies of the Gulf aimed to bolster security after the 1979 Islamic revolution in Iran which was followed by an eight-year war between Baghdad and Tehran.