WASHINGTON (Reuters) - The United States on Thursday said it condemned Russian efforts to use energy as a "tool of coercion" in its dispute with Ukraine.

U.S. State Department spokeswoman Jen Psaki said Russia had reneged on an agreement with Ukraine that offered reduced natural gas prices in exchange for a 25-year lease on Black Sea fleet facilities.

"We condemn Russia's efforts to use energy as a tool of coercion against Ukraine," she said. "Ukraine is now paying $485 (1,000 cubic meters), a price clearly not set by market forces and well above the average price paid by EU members.

"The United States is taking immediate steps to assist Ukraine, including the provision of emergency finance, technical assistance in the areas of energy security, energy efficiency, energy sector reform."

Russian President Vladimir Putin on Thursday warned European leaders that Russia would cut natural gas supplies to Ukraine if it did not pay its bills and said this could lead to a reduction of onward deliveries to Europe.

Russia, a key provider of natural gas, recently annexed the Crimea region from Ukraine.