The six-nation Gulf Cooperation Council (GCC) has made much progress to clear the last obstacles for the bloc's long-awaited customs union but total completion will take two to three years, Kuwait's finance minister said.

The introduction of a customs union in 2003 had been hailed by officials as a major achievement, countering critics' claims that the Gulf Arab bloc consisting of Saudi Arabia, the United Arab Emirates, Kuwait, Qatar, Bahrain and Oman would be unable to realise economic integration in the world's biggest oil exporting region.

But differences remain and trucks transporting goods have been held up for days mainly at the border between Saudi Arabia and the United Arab Emirates, an issue which has cast fresh doubt over the efficiency of the customs union plan.

"I don't say there are obstacles in the way of implementing the agreement but there are different opinions among us," Mustapha Al-Shamali, whose country holds the rotating Gulf presidency, told reporters after a meeting of Gulf finance ministers in the Saudi port city of Jeddah late on Monday.

"We need more time to implement the remaining items," he added, citing the need to work out details for applying some custom duties among other issues.

The GCC's attempts over the past 29 years to emulate the European Union's economic integration model have been dogged by delays in a monetary union plan and regional rivalry and mistrust between its two biggest economies, Saudi Arabia and the United Arab Emirates.   

Shamali also said the finance ministers did not discuss the planned GCC monetary union, but that the establishment of a joint Gulf central bank was on its way.

"The brothers, the central bank governors, continue their meetings regarding this," he said.

Saudi Arabia, Kuwait, Qatar and Bahrain are pursuing the long-delayed monetary union project after the United Arab Emirates withdrew in 2009, three years after Oman did the same.

The four states launched the forerunner for the joint central bank in March. The head of the Saudi Arabian Monetary Agency, Muhammad Al-Jasser, is the chairman of the council and Rasheed al-Maraj, the central bank governor of Bahrain, his deputy. - Reuters