EPA Administrator Lisa Jackson deflected questions today about when -- or if -- she would respond to a letter that Sen. Lisa Murkowski, R-Alaska, sent her Friday asking more questions about her agency's plans to regulate greenhouse gas emissions.

"I don't have a date yet," Jackson told reporters after speaking at a National Press Club luncheon. "I haven't had a chance to review it yet."

Murkowski, the top Republican on the Energy and Natural Resources Committee, was following up on the questions Sen. Jay Rockefeller, D-W.Va., and several other coal-state Democrats asked EPA in a letter last month. Specifically, Murkowski asked about the "tailoring" rule: what types and sizes of stationary sources will be required to get Clean Air Act permits, and when the regulations would be rolled out.

Rockefeller sent his letter on a Friday afternoon and got a response the following Monday evening. The discrepancy has not gone unnoticed by Murkowski's office. "Senator Rockefeller was able to get a response in three days; I think Senator Murkowski would like the same treatment," Murkowski spokesman Robert Dillon said today.

In interviews after her response to Rockefeller, Jackson noted that letter was sent by "senators of my own party who expressed some real concerns about EPA's actions." She also played up the urgency of responding to senators "who we all know are trying to talk about the need of energy legislation, asking those kinds of fundamental questions. I wanted to get an answer -- as much of an answer as we could get back."

Murkowski has expressed more of a willingness to support comprehensive climate and energy legislation than most other members of her caucus. But she has also been ruffling feathers at EPA over her plans to introduce a disapproval resolution stripping the agency of its regulatory power over greenhouse gas emissions. The legislation Rockefeller introduced wouldn't go as far, only delaying EPA regulation of stationary sources for two years.

Jackson has repeatedly said that Murkowski's resolution would hurt the administration's goals of reducing emissions, especially in the transportation sector.

Darren Goode contributed to this report.

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