This could get interesting, although in the case of Bahrain and SA, it's really just formalizing something that is already occurring. But I'm curious about which is the "3rd country".
"Saudi Arabia and Bahrain are expected to announce closer political union at a meeting of Gulf Arab leaders on Monday, a Bahraini minister said, in a move dismissed by the opposition as a ruse to avoid political reform.
..."I expect there will be an announcement of two or three countries. We can't be sure but I have a strong expectation," Samira Rajab, Bahrain's minister of state for information affairs, told Reuters on Sunday. Two of the countries mentioned were Saudi Arabia and Bahrain; Rajab did not name the third.
"Sovereignty will remain with each of the countries and they would remain as U.N. members but they would unite in decisions regarding foreign relations, security, military and economy.""