WASHINGTON (AFP) - The White House on Friday played down the risk posed to the European economy by Russia's threat to cut off gas supplies to Ukraine, insisting the region has adequate stocks.

"There is no indication currently that there's much risk of a natural gas shortage in the region," President Barack Obama's spokesman Josh Earnest told reporters from aboard Air Force One.

Russia is Europe's biggest single energy supplier and its natural gas pipelines mainly run through Ukraine, where some is used and some passes through to major western economies such as Germany.

European stock markets tumbled on Friday after Russian energy giant Gazprom warned it could cut off gas exports if the new authorities in Kiev do not pay a debt of $1.89 billion.

The move was seen as an attempt to strongarm Kiev into backing down in the political stand-off that began last month when a popular revolt overthrew Ukraine's pro-Moscow leader Viktor Yanukovych.

But Washington, which backs Ukraine's new government and opposes Moscow's moves to seize the Crimean Peninsula, said any gas embargo would hurt Moscow as much as Kiev.

"Russia relies on revenue from exporting natural gas and other sources of energy," Mr Earnest said.

"Russia currently yields about $50 billion a year in revenue from exporting natural gas, so ending that kind of relationship with Europe would have significant financial consequences for Russia as well." The White House spokesman confirmed reports that Europe currently has above-average inventories of liquefied natural gas in storage after an unusually mild winter.

And he suggested that Russia would not want to damage its reputation as a reliable energy supplier.