UPDATE 1-Greenland delays decision on Alcoa plant

* Investment nod put back to Spring 2010

* Scales back likely involvement

* Says more studies needed on construction costs

By Teis Jensen

COPENHAGEN, July 15 (Reuters) - Greenland has delayed a decision on joining Alcoa Inc (AA.N) in a planned aluminium venture and scaled back its possible stake to 10 to 30 percent.

The chief executive of state body Greenland Development said more time was needed to estimate construction costs at the smelter and hydropower venture in Maniitsoq.

"It has been postponed because we haven't finished the field investigations yet," Flemming Drechsel told Reuters on Wednesday.

Greenland's parliament will decide on the venture in spring 2010 and not this autumn as earlier planned.