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The Navajo reconsideration “has been in keeping with a steady drumbeat of announcements since Jan. 20 in which most of the clean air rules by the Bush administration that I have been fighting have been lined up and announced for reconsideration,” Mr. Walke said.

He stressed that Mrs. Jackson’s moves are closely coordinated with the White House as part of Mr. Obama’s anti-global warming agenda. The decision this week to review three rules affecting fine particle industrial pollution under the “new source review” authority of the Clean Air Act was part of the same approach.

“For government officials to talk about green jobs, clean energy and global warming action in the same breath is a novelty and overdue recognition in our view,” he said.

Conservative-leaning and pro-business groups are keeping a close eye on the reinvigorated EPA and are noticing that the agency is inclined to find common ground with environmental groups.

“There’s a lot of things they’ve wanted to do that have been accumulating over the years and now there is a chance to implement them,” said Ben Lieberman, a senior policy analyst at the conservative Heritage Foundation.

Mr. Lieberman said Mrs. Jackson has proceeded with a dose of cautionbecause of the recession. On the greenhouse gas finding, he said only worries about hurting the already ailing economy kept Mrs. Jackson from proposing new auto and truck emissions regulations more rapidly.

William Kovacs, vice president for the environment, technology and regulatory affairs at the U.S. Chamber of Commerce, said it would be only harder, if not impossible, to put new coal-fired power plants into service because of EPA decisions this year.

Between 60 and 70 plants have been stalled because of permitting issues, he said, and challenges to clean energy projects over environmental issues are likely as well.

“It’s like the proverbial floodgates at the dam,” he said. “They’re just opened.”