* Ellaktor leads Alysj joint venture in Qatar deal
* Joint venture to build subway line in Doha
* Greece's biggest builder expands abroad to offset local slump
ATHENS, April 24 (Reuters) - Greece's biggest construction group Ellaktor said on Thursday it signed a 3.2 billion euro ($4.4 billion) contract to build a subway line in Qatar.
Ellaktor, which has been expanding its foreign business to cope with an economic crisis at home, said in an Athens bourse filing it owned a 32 percent stake in joint venture Alysj, which won the "Gold Line Underground" project in Qatar's capital city of Doha.
Construction of the 32-kilometre long tube is expected to be completed in 2018, Ellaktor said, boosting the company's construction backlog of currently 3 billion euros. The firm did not reveal its joint venture partners in the Qatar project.
Foreign operations, mainly in the Balkans and the Middle East, account for about a third of the company's backlog.
Once a major driver of the Greek economy, construction has slumped by more than 75 percent due to austerity policies imposed on bailed-out Greece by its international lenders.
But the prospects of Greece's construction industry are improving after public finances stabilised and the country returned to bond markets earlier this month.
Titan, the country's biggest cement maker, said it expected demand for cement to grow this year for the first time since 2006, on the back of public investment.
Ellaktor is participating in a 7.6 billion euro toll road project that Greece unfroze in recent months. ($1 = 0.7231 Euros) (Reporting by Angeliki Koutantou; editing by Harry Papachristou and Elaine Hardcastle)