UPDATE 2-Turk PM wants Iran, Russian gas in Nabucco

* Turkey says Iran should be included in Nabucco

* Azerbaijan says interested in Nabucco

* Turk PM says Russia gas can be transported too

ANKARA, July 13 - Turkey's Prime Minister Tayyip Erdogan said on Monday Turkey wanted Iranian gas to be transported to Europe via the planned Nabucco pipeline "when conditions allow", despite U.S. opposition.

European Union governments and Turkey were to sign transit agreements in Ankara later on Monday for the EU and U.S.-backed Nabucco pipeline, which aims to reduce Europe's energy dependence on Russia by transporting gas from the Caspian and Middle East through the planned pipeline from 2014.

"We desire Iranian gas to be included in Nabucco when conditions allow," Erdogan told a gathering of Nabucco partner countries and regional countries including Iraq and Georgia.

U.S special energy envoy Richard Morningstar on Sunday reiterated Washington's opposition to possible use of Iranian gas in Nabucco until Washington normalises relations with Tehran. The two are at odds over Iran's nuclear programme.

Transit countries Turkey, Bulgaria, Romania, Hungary and Austria will sign the accord later on Monday after years of delay, giving the 7.9 billion euro project a major political boost. But questions over supply and financing still plague its feasibility and as progress of a rival Russian plan edges ahead.

NO CONCRETE DEALS ON SUPPLY

No concrete supply deals have yet been signed for Nabucco, which plans to pump 31 billion cubic metres of natural gas to Europe by 2014.

The Nabucco Consortium has mentioned Egypt, Azerbaijan and possibly Russia and Turkmenistan as sources for gas.

Azerbaijan's Industry and Oil Minister Natik Aliyev told the gathering that Azerbaijan was interested in Nabucco and that the gas-rich Caspian country wanted diversification of its energy export routes.

Iraq's Prime Minister Nuri al-Maliki said Europe could receive 15 billion cubic metres of Iraqi gas via Turkey, but it was not immediately clear if he was referring to Nabucco.

On Sunday, Iraqi government spokesman Ali al-Dabbagh said Iraq did not have any surplus gas to sell via U.S-backed Nabucco pipeline now.

Egypt's Oil Minister Sameh Fahmy also said a planned Arab gas pipeline could be a potential source of gas for Nabucco.

Erdogan also said he believed Russian gas could be transported to the European markets via Nabucco.

The Nabucco project has been unable to find sufficient throughput for the 31 billion cubic metre pipeline, which is competing with the rival Russian-backed South Stream project to feed growing European consumption.

Analysts say Russia's Gazprom more practical strategy -- signing basic cooperation agreements with supplier countries -- gives South Stream pipeline a competitive edge by building relationships between companies.

The European Union has supported the project as a way of reducing its reliance on Russian gas. A row over prices and debt between Moscow and Kiev last winter led to Russia cutting off supplies into Ukraine, including those destined for Europe.

Predominantly Muslim Turkey, which aspires to join the European Union, hopes Nabucco will strengthen its position as an energy hub for the West and advance its EU bid.