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Qatar's finance minister says a new unified value-added tax across the Gulf Arab countries could come into effect as early as next year as the oil-rich region searches for new sources of revenue.

Ali Sherif al-Emadi told reporters Tuesday that all six members of the Gulf Cooperation Council had signed onto the agreement. The bloc includes Bahrain, Kuwait, Oman, Qatar, Saudi Arabia and the United Arab Emirates.

Al-Emadi says a Jan. 1 implementation date could be delayed a year if countries need more time to prepare. He gave few details, but an earlier framework agreement calls for a 5 percent levy on some goods.

Gulf budgets have come under strain due to a slump in energy prices and increased spending and population growth.