Jason Burnett, the former associate deputy administrator of the Environmental Protection Agency who resigned last month over the Bush administration's unwillingness to address greenhouse-gas emissions, provided more details to a Senate panel Tuesday about how top White House officials worked to quash new regulations on greenhouse gases.

Appearing before the Senate Environment and Public Works Committee, Burnett shared with senators some of the behind-the-scenes negotiations that took place regarding the agency's response to Massachusetts v. EPA and the decision to deny California a waiver to set higher automobile emissions standards.

Burnett said EPA officials -- including Administrator Stephen Johnson -- told the Bush administration that California officials should be permitted to establish air-quality standards on their own. Johnson supported a partial waiver for several years, but President Bush rejected his suggestions, arguing that he wanted a "single, national standard."

Burnett also testified that the EPA's experts, acting in response to the Supreme Court's direction from April 2007, agreed last December that greenhouse gases were a risk to human health and should be regulated under the Clean Air Act. But as Burnett had told Grist previously, the administration decided to ignore those findings and instead extend the period of public comment on their rulemaking proposal.

"The concern was that moving forward would mean an increase in regulation, and that was not something that this president wanted to have associated with him," said Burnett.