ST. PETERSBURG, June 5 (RIA Novosti) - A reasonable minimum price for oil is $75 per barrel, Russia's first deputy prime minister said on Friday, adding that production could drop in Russia if the credit crisis persists.

"We need at least $75 per barrel," Igor Sechin said on the sidelines of the International Economic Forum in St. Petersburg, the country's largest investment event.

"Output will not drop in the next few years," Sechin said, citing major investment in the industry in recent years, but he warned that "an increasingly shrinking access to finances could lead to a decline."

Oil prices plummeted from a record $140 a barrel last July to around $35 over shrinking demand amid the global financial crisis. Prices have strengthened in the past three months, along with stock markets, rising to above $68 a barrel on Thursday, fueling expectations that crude will continue its rally.

But Sechin said it is not clear so far whether the price hike is a result of fundamental changes in the world economy or of market speculation.

Speaking later on Friday at the forum's session focusing on crude prices, Sechin said prices could again begin to decline. He also urged major investment in oil prospecting and production, warning that prices could surge to $150 a barrel in two or three years' time.

"If investment is not restored, the forecast of $150 per barrel in two or three years' time could prove realistic," Sechin said, referring to a figure earlier cited by OPEC.

Oil has been a major source of revenue for Russia, the largest non-OPEC producer, fueling its almost decade-long economic boom before the global credit crunch hit the country.