Russia's finance minister has promised to maintain a tight lid on spending as the country faces its worst economic downturn in 15 years.

Anton Siluanov said an earlier plan to boost government spending by nearly 12 percent this year is unrealistic, and some of the planned expenditures should be cut.

He told an economic forum Wednesday that if oil prices average at $50 a barrel this year, government revenues will drop by around $45 billion compared to an earlier plan.

The Russian ruble lost about half of its value last year under the combined blow of slumping global prices for oil and Western sanctions over Ukraine. The currency dropped about 1 percent in morning trading in Moscow, nearing 66 rubles per dollar.