INTERVIEW-Turkey to decide on Iran gas investment in 2 weeks

* Eyes future Iraq oilfield tenders with Gazprom, U.S. firms

* Plans to finish gas grid privatisations this year

(Adds details, background)

By Orhan Coskun

ANKARA, March 24 (Reuters) - Turkey will decide within two weeks on whether to go ahead with investment in Iran to produce natural gas, in a deal that would upset the United States.

Energy Minister Taner Yildiz said late Tuesday the deal, with an estimated worth of $5.5 billion, had political support in Ankara.

The decision to press ahead now rested with firms carrying out feasibility studies in the South Pars gas field, Yildiz told Reuters in an interview.

The United States is seeking to isolate Iran over its nuclear programme, which the West fears includes covert ambitions for nuclear weapons. Washington is lobbying Turkey and other countries to support the threat of economic sanctions.