The slogan, made famous by Iran's revolutionary leader, Ayatollah Ruhollah Khomeini, highlights the country's new drive to tap its oil riches on its own — without Western investment or technological know-how — as Iran faces a threat of tighter U.N. sanctions and American financial pressure over its nuclear ambitions.

The Azadegan field in southwestern Iran showcases the bid: the first major field to be developed solely by Iranian companies. Pumping began in February in the vast oil basin — off limits to the public, but The Associated Press received permission to tour the site recently with a government escort.

The self-sufficiency drive has become a vital test of how well Iran can ride out more Western sanctions — and possibly rake in billions of dollars more in oil revenues as prices hit record highs. It also is shaping up as a political gamble for hardline President Mahmoud Ahmadinejad, the main proponent of using local firms.

Some lawmakers and outside experts contend that Iranian companies will take longer and get less oil than foreign investors often with better technology and project management.

Among the challenges that could frustrate Iranian oil engineers: dealing with high-pressure fields, elevated sulfur content in the crude and water levels inside the wells.