Europe aims to advance the Southern Corridor of energy projects to alleviate energy security concerns. Apart from Nabucco, the project includes the proposed White Stream to Romania and Ukraine and the Trans-Adriatic pipeline.
Richard Morningstar, the U.S. special envoy for Eurasian energy, told Russia's business newspaper Kommersant that the entire Southern Corridor was vital for European energy security.
"We support not only Nabucco but also the entire (Southern) Corridor -- a series of pipelines that will be required to deliver Caucasian and Central Asian gas to Europe via Turkey," he was quoted as saying.
Morningstar noted, however, that Washington "preferred Nabucco," adding that Iraq and Turkmenistan were likely suppliers for the pipeline.
Iran, he added, will play no role in European energy projects despite the vast amount of natural gas reserves in the Islamic republic.
Europe aims to break Russia's grip on the energy sector through Nabucco, though the project is slow to convince potential suppliers to commit.