Critics have blasted Russia’s $15 billion financial aid to Ukraine, signed this week as proof Ukrainian President Viktor Yanukovich is aligning his country with Moscow instead of the West.

While Ukrainian officials say it will guarantee their financial stability, the opposition is concerned this deal will only expand Russia’s influence over the region.

The possibility of Ukraine signing an economic deal with the European Union concerns Russian President Vladimir Putin, according to Fiona Hill, a senior fellow at the Brookings Institution.  

“This was a real challenge to the Russians because at the same time Putin has for the past couple of years been trying to expand a customs union [in the region],” said Hill.

Hill says the customs union is only a cover for Moscow’s interests.

“[It] would extend to a larger region that would support Russian jobs, Russian products … and cement Russia’s influence, economically and politically over many of the states that used to be a part of the U.S.S.R,” said Hill, author of “Mr. Putin: Operative in the Kremlin.”

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According to Hill, “it’s really a battle of the future perspective and direction of these countries.”

One issue that Russia has been able to hold over Ukraine is the price the country pays Moscow for natural gas.

“We’ve been in this ‘gas politics’ for a long time now … so what the Russians have given to the Ukraine is the opportunity to buy gas at a reduced price,” said Hill.

Ukraine might need Russia, but Moscow also needs Kiev, said Hill. “The direction that Ukraine goes in is pretty important economically and politically for the future prospective of Russia.”

Chris Snyder is a producer for FoxNews.com based in New York. Follow him on twitter: @ChrisSnyderFox