Wiesbaden, Germany  - Social Democrats (SPD) moved a step closer Saturday to ousting Chancellor Angela Merkel's Christian Democrats (CDU) in the German state of Hesse and forming a government with the help of a far-left party.

A regional SPD congress approved plans for a minority coalition with the Greens and asked party leader Andrea Ypsilanti to stand for election as premier in the regional legislature on November 4.

If the incumbent CDU premier in Hesse, Roland Koch, is toppled, it would be a further blow to Merkel's CDU after its sister party in Bavaria, the Christian Social Union, lost its absolute majority in state elections on September 28.

A victory for Ypsilanti would also likely strain the chancellor's federal coalition with the SPD, one year before the September 2009 general election in Germany.

The CDU has accused Ypsilanti of breaking a pre-election promise not to ally with the Left, which embraces former East German communists and disgruntled Social Democrats from the west.

Koch narrowly lost a state legislative election nine months ago. As caretaker premier since, he has sought to weaken the three competing parties which oppose him and has criticized their plans for a loose alliance to vote him out of office.

In the state capital of Wiesbaden, Ypsilanti said the coalition agreement with the Greens would promote investment in renewable energy and delay expansion of Frankfurt's airport by about eight months. The Greens are opposed to expanding the airport on environmental grounds.

Some 95 per cent of the delegates at the regional congress gave their backing to Ypsilanti. The coalition plan still has to be approved by the Greens as well as the Left, whose leaders have agreed to tolerate an SPD-led government.

Ypsilanti's first attempt to form an alliance with the Left failed because of opposition within her own ranks and later let to the resignation of SPD chairman Kurt Beck, who had come under fire for backing the move.

Ypsilanti, 51, would not be Germany's first woman state premier, but follows in the Social Democratic footsteps of Heide Simonis, who ran the state of Schleswig-Holstein from 1993 till 2005. (dpa)