MOSCOW, April 7 (Reuters) - Russia's federal budget balance sank to a deficit of 2. Elina Ribakova, a Senior Fellow at Bruegel and the Peterson Institute for International Economics, said the deficit will be closer to 4% or 5% of GDP, with Russia's finance technocrats the main obstacle to an even wider gap from opening up. The central bank has repeatedly warned that the budget deficit poses inflationary risks and may compel it to raise interest rates from the current 7