Europe aims to break the Russian grip on the European energy sector through the so-called Southern Corridor of transit networks that includes the Nabucco pipeline.
Richard Morningstar, the U.S. envoy for Eurasian energy, said during a Black Sea energy conference in Turkey that Washington considered Iraq's participation in the Nabucco pipeline integral to the project.
"We believe it is important and Turkey believes it is important that the Kurdish gas will ultimately be able to go north and to the Southern Corridor," he was quoted by Turkish daily newspaper Today's Zaman as saying.
The Nabucco consortium in Vienna said it confirmed and ordered the engineering work for feeder lines from Georgia and Iraq to connect to the main artery in Turkey.
Energy deals in Iraq require mutual agreements between the central government in Baghdad and the regional Kurdish government in Erbil. Morningstar said he hoped both sides would agree to the Nabucco terms to move the project forward.
"We recognize that this (Kurdish participation) cannot and should not happen without an agreement between Baghdad and Erbil," he said. "We hope that this will occur."