Philipp Maystatt, president of the European Investment Bank, told the meeting his institution could underwrite about a quarter of the euro7.9 billion project.
And Thomas Mirow, president of the European Bank for Reconstruction and Development, said his bank was "ready to examine the case for a financial contribution to the pipeline."
Other participants — prime ministers and other government representatives from European countries — expressed hope that the governments and commercial companies involved would be able to complete plans by late spring, allowing construction to start shortly after.
Even if conditional, the backing is significant for a project whose difficulties in attracting investors have only increased due to the world economic downturn
The EU, backed by the United States, has proposed the 2,050-mile (3,300 kilometer) Nabucco pipeline to transport gas from Azerbaijan and Turkmenistan, through Turkey and across the Balkans to Central Europe.
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But since its inception seven years ago, the project has been mired in doubt about availability of non-Russian gas to supply it. That, in turn has dampened investor interest — a delay exploited by Moscow and Beijing to lock in gas from Central Asia, the projected source for Nabucco.
Last year's Russia-Georgia conflict added to the uncertainties. The line would either have to transit Georgia or originate in Iran — an unpopular option at a time the West is pressuring Tehran to abandon its nuclear program.
And even if Europe could secure a route for Nabucco and fill it with gas, it would still carry only about six to eight percent of Europe's gas demands by 2020.
Further muddying the waters, Russia proposed another pipeline in June 2007, called South Stream, which would ship about 30 billion cubic meters of the gas essentially the same route as Nabucco.
In a dig highlighting Russia's gas superiority, Moscow's ambassador to the EU, Vladimir Chizhov on Monday said the only difference is "that South Stream has gas and Nabucco seems not to have gas.
Russia already supplies Europe with about a quarter of its gas needs, through pipelines it also controls — a point most recently driven home when Gazprom supplies through Ukraine were halted as the year began.
Adding his support as head of the EU's rotating presidency, Czech Prime Minister Mirek Topolanek warned participants that "our freedom and independence are at stake" in breaking Europe's energy dependency.
"The more we are dependent on one source ... the more susceptible we are to blackmail and the narrower our political options become," he said, urging all 27 EU members — and the EU Commission in Brussels — to fully back Nabucco.
In a written message to the meeting, Commission president Jose Manuel Barroso said he also supported the project.
Among other political leaders at the Nabucco talks was Premier Sergei Stanishev of Bulgaria — where tens of thousands endured chilly homes as gas from Gazprom, their only source, trickled to a stop before being restored last week.
So is President Ilham Aliyev of Azerbaijan and senior figures from other gas-rich central Asian countries as well as Iraq, which sits on an estimated 3.1 trillion cubic meters of natural gas reserves — the world's 10th largest.
Topolanek described the Nabucco project as a "big test" for the EU's ability to act as one in its own interest.
"If the EU as a whole doesn't back this project ... then it will be very, very difficult, no impossible, to implement," he told The Associated Press.