Argentina state-owned oil firm YPF eyes $2 bln debt sale boost

* Company aims to invest $7 bln a year to boost output

* Needs financing, plans 3.5 bln peso local bond issue

BUENOS AIRES Aug 15 (Reuters) - Argentina's biggest energy company, state-controlled YPF, will ask shareholders to authorize debt sales of up to $3 billion to finance investment, the company told the local securities market regulator on Wednesday.

This would represent a $2 billion increase over the current debt program approved in June 2008 and would help the company make headway towards its goal of investing $7 billion a year to boost flagging oil and natural gas production.

YPF said it will propose the change at a Sept. 13 shareholders meeting. Last week, the board of directors approved local bond issues worth 3.5 billion pesos ($760 million) under the 2008 shelf registration.

Argentina's government seized a controlling stake in YPF from Spain's Repsol in May, renationalizing a company that had been state-run before the 1990s. Repsol has vowed to fight Argentina if it does not receive just compensation.

President Cristina Fernandez accused Repsol of not investing enough to sustain oil and gas production as energy demand surged. This translated into a rising bill for costly fuel imports, affecting the country's trade surplus. ($1 = 4.6075 Argentine pesos) (Reporting by Alejandro Lifschitz; Writing by Hilary Burke Editing by; W Simon)