At this huge oil field in southwest Iran, one building stands out among the pumps and maze of pipelines: On its roof in giant letters, big enough for satellites or pilots to see, are the words: "We can do it." 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 UN 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 with better technology and project management.