DUBAI Oil supermajor Exxonmobil aims to build on its Saudi success story by playing a leading role in the kingdom's multi-billion dollar gas investment opening.

"Exxonmobil is clearly interested in taking a leadership role and being a significant investor in the gas initiative," Daniel Nelson, chief executive officer of Exxonmobil Saudi Arabia, told Reuters in a telephone interview on Monday.

"However, we have received no advice from the Saudi government concerning a leadership role and it would be inappropriate to comment on that at this time."

Nelson was responding to suggestions from industry sources on Sunday that the U.S. energy giant could get top billing in two of the three so-called "core venture" gas deals on offer.

Big oil companies have been vying for a stake in Saudi Arabia's upstream gas sector, off limits to them since nationalization in 1975, ever since Crown Prince Abdullah hinted at investment possibilities in 1998.

The industry sources told Reuters that Exxonmobil, the world's biggest energy company, could secure a top slot in the largest project worth an estimated $15 billion -- core venture 1 (south Ghawar) -- as well as in core venture 2 (Red Sea).

European giant Royal Dutch/Shell is tipped to lead core venture 3 (Shaybah), the sources added.

Nelson was upbeat about Exxonmobil's prospects in the race.

"These projects have the potential to create a world-class domestic energy infrastructure in Saudi Arabia and we are optimistic that Exxonmobil can play a positive central role in the effort, working in cooperation with others in the kingdom."