The United States has an obligation as an "energy superpower" to respond to Russian pressure on the Ukrainian gas sector, U.S. Rep. Fred Upton, R-Mich., said.

Upton, chairman of the House Energy and Commerce Committee, said threats from Moscow to shut off the supply of natural gas through Ukraine because of lingering debt were shameful.

"Threatening to turn off the spigot of natural gas to Ukraine is nothing but extortion playing out on the global stage," he said in a statement Thursday.

Russian President Vladimir Putin said Ukraine will have to pay in advance for its natural gas supplies because of accumulating gas debt. He added Thursday, however, that he was open to discussing ways to normalize the situation with his European counterparts.

European consumers get about a quarter of their gas needs met by Russia, though most of that supply runs through the Soviet-era transit network in Ukraine.

Upton said, with U.S. natural gas production growing, the government has a responsibility to address the issue.

"As the world's emerging energy superpower, America has a newfound responsibility to help our allies," he said.

He helped introduce legislation that would facilitate U.S. natural gas exports, though it's the private sector that determines export destinations.

The United States has no free-trade agreements with European countries.