Despite the Bush administration’s position to back a voluntary approach to controlling carbon emission, a U.S. energy official has told an international conference on biofuels that the U.S. is moving towards the regulation of such emissions, Associated Press reports.

“There will be carbon regulation of some sort,” AP reports Dan Arvizu, director of the National Renewable Energy Lab of the Department of Energy, as saying. “I am neutral as to which kind of carbon management regulation there will be. It is very clear to me that there will be carbon management, whether it will be a direct tax, carbon cap-and-trade or some other instrument.”

Arvizu did not say he was speaking for the Bush administration. But according to AP, some listeners thought it was significant that he spoke a week after briefing President Bush’s global warming conference of major carbon-emitting nations.

“The position of this administration is beginning to evolve,” Arvizu later told the AP.