The project is designed to bring central Asian gas to Europe via Turkey, Bulgaria, Romania and Hungary. Supporters say it is vital to wean the region from over-dependence on Russian energy.
"I encourage my Turkish friends to engage now seriously in the discussions in view of making Nabucco operational as of 2013," said Olli Rehn, the EU's Enlargement Commissioner.
"Too much time has already been wasted on arguing rather than making things happen," Rehn was quoted as saying by Reuters.
Analysts have criticized Turkey for dragging its feet at the bargaining table to try to secure higher transit fees and rights to trade gas going through the pipeline, due to supply an annual 30 billion cubic meters of Caspian or Middle Eastern gas.
But some observers say hopes of construction are quickly fading, especially after the conflict in Georgia increased doubts about the security of investing in the turbulent region.
THE U.S. EXTENDS SUPPORT
A U.S. official said Friday that a deal may be reached soon allowing natural gas from ex-Soviet nations to reach western Europe without crossing Russian territory.
The U.S. special envoy for Eurasian energy issues, C. Boyden Gray, told reporters in Rome that an agreement on a pipeline could be completed in as soon as six months, the Associated Press reported.
"I think there will be an understanding for transit through Turkey for a pipeline," Gray said, without elaborating. "Completely firm details and shovels underground no, but the outlines of a deal, yes."
Gray did not specify what pipeline, but appeared hint at the TGI pipeline project linking Greek and Turkish gas networks that would allow Azerbaijan to export gas to Italy by 2012.
U.S. officials have supported TGI as a way of easing Russian energy dominance in Europe.
Gray also said the Nabucco pipeline, which would deliver gas from Turkmenistan and other Central Asian and Caspian countries westward through Turkey while bypassing Russia, will "eventually" be built.
"The reality is that there is enough gas in the Caspian to fill much more than TGI and Nabucco," he said.
The project, however, has been slowed by high costs and uncertainty over sources of supply, and Russia is promoting rival routes through its territory as a cheaper and safer alternative.