Russia's oil wealth funds lost $13 billion in value over the last month, falling to about $193 billion, as Russia taps into the cash pot to cover its budget deficit, the Finance Ministry said Monday.

The Reserve Fund, designated for plugging holes in the federal budget, is currently worth 3.6 billion rubles ($106.81 billion), down from 4.1 trillion rubles on April 1.

Russia is expected to post its first budget deficit in a decade this year, of about 3 trillion rubles, as the economy slips into recession and oil prices remain low.

The Finance Ministry said dollars, euros and sterling from the Reserve Fund were converted into a total of 400 billion rubles in April, and the money was transferred into the federal budget, taking the value of the transfers to date to 1 trillion.

The Reserve Fund is expected to run out by the end of next year, while budget deficits last until at least 2011.

The second outlet for Russia's oil revenues, the National Welfare Fund, held broadly steady at 2.9 trillion rubles ($86.3 billion). The fund is designated for longer-term projects, although officials have said some of the money could be used to plug a deficit in the state pension fund.