Commercial traffic has resumed on the strategic Shatt al-Arab waterway after 31 years, with the official opening of a port for oil giant Shell, an Iraqi official said on Tuesday.

Part of the 200 kilometre (120 mile) long waterway forms a section of the border with Iran. An unresolved boundary dispute was a major reason cited by now-executed dictator Saddam Hussein for the 1980-88 war with Iran, which resulted in the waterway's closing.

"The Shatt al-Arab is reborn again after being closed for 31 years," Mehdi Badah Hussein, the head of the joint committee to develop Majnoon oil field, told AFP at a ceremony to open the port.

"There are other harbours on the Shatt al-Arab, but commercially, this is the first time Iraq succeeded in turning the Shatt al-Arab into a maritime passage which will help in transporting heavy equipment," Hussein said.

A consortium of Anglo-Dutch oil giant Shell and Malaysia's Petronas signed a contract with Iraq in January 2010 to operate the enormous Majnoon field.

"We believe this is the first jetty harbour to bring in ships that can come from all over the world back off the river with heavy equipment in 31 years," Shell Majnoon general manager Ole Myklestad told AFP.

"This is very important," Myklestad said during the ceremony, as it is the first time in decades that a commercial harbour was opened here.

He said the first ship arrived to the harbour on January 5.