MOSCOW, Feb 6 (Reuters) - Slumping energy revenues and soaring expenditure pushed Russia's federal budget to a deficit of 1. 4% lower at 426 billion roubles in January than in the same month last year, which it put down primarily to lower prices for Russia's Urals blend and lower volumes of natural gas exports. 5 billion roubles worth of Chinese yuan and gold spent in January to cover the deficit