'There will be a southern corridor, but Iranian gas will not be part of it,' Ambassador Richard Morningstar says.

A proposed southern corridor gas route will not use any Iranian natural gas in the near future due to a row over Tehran’s disputed nuclear program, according to a top U.S. official.

"There will be a southern corridor, but Iranian gas will not be part of it," Ambassador Richard Morningstar, special envoy of the U.S. Secretary of State for Eurasian Energy, said during the Black Sea Energy and Economic Forum in Istanbul on Thursday.

"Nabbucco could be the most profitable project of the southern corridor, if it runs at full capacity," said Morningstar. "Big ideas need to be bankable, however."

There is some concern that without Iranian gas, Nabbuco would not be able to operate at full capacity.

Asked to comment about the U.S. position regarding Iran, Turkish officials implied that the chances of realizing Nabucco would be even weaker if Tehran is ruled out.

"We certainly think that Iraqi gas could be a contributor to the southern corridor and a contributor to Europe. There is a lot of potential gas in northern Iraq. There is actually gas all over Iraq," Morningstar told a group of reporters. "But with respect to northern Iraq, that will require some kind of an agreement between Baghdad and Arbil on revenue-sharing and how the resources are developed."

The process of forming a government is still ongoing in Iraq, as uncertainty persists. “Hopefully, when a new government is formed, these issues will be resolved,” Morningstar said.

The official did not rule out the option of Qatari gas for Nabucco. "It is one of the options," he said.

Different pipeline projects, such as Nabucco and South Stream, “do not compete with each other in the long run,” according to Turkish Energy Minister Taner Yıldız.

John Roberts, an energy security specialist for Platts, agreed with Yıldız’s long term viewpoint but added that for more than one project to go ahead, Azeri and Iraqi gas would have to be fully utilized due to the need to meet the combined pipelines’ potential