Former Environmental Protection Agency chief Christine Todd Whitman said President Bush missed the “perfect opening” to call for a cap on greenhouse gas emissions in his State of the Union address Tuesday night.

While such a move would have represented a major policy shift for the administration, Whitman said she had hoped the fact that 10 major American companies called for a cap earlier this week would have provided sufficient political cover.

Those companies, which include General Electric, DuPont and Alcoa, joined four non-profit groups that have advocated for limits on emissions of carbon dioxide and other greenhouse gases to form the U.S. Climate Action Partnership. The group backs government-imposed limits on greenhouse gas emissions, but is not backing a specific policy proposal.

In the days preceding the State of the Union, a rumor circulated that Bush might change course, but Press Secretary Tony Snow denied that would happen.

While Bush did not call for a carbon cap, Whitman, who as EPA director often butted heads with White House officials over the need to address global warming, credited her former boss for acknowledging the climate was changing in his State of the Union address Tuesday night. The president called global climate change a “serious challenge.”

“That’s not insignificant,” Whitman said, given how carefully the speech is vetted.

The slight concession in Bush’s speech, along with recent comments from the Council on Environment Quality Chairman James Connaughton, seem to suggest the White House is willing to work with Capitol Hill on global-warming bills and leaves Whitman “more and more hopeful” that a greenhouse gas emissions measure could be passed.

Support from big business and some evangelical groups may put the White House in a “position to accept a cap on carbon,” if not actively push for one, Whitman said.

Whitman, who was governor of New Jersey prior to joining the Bush administration, now heads a coalition with a Greenpeace founder, Patrick Moore, that is pushing for further development of nuclear power. The group is called Clean and Safe Energy, or CASEnergy.

Nuclear power plants do not produce greenhouse gases, and any carbon cap likely would benefit the nuclear-power industry. The process of using nuclear power to produce electricity does leave radioactive spent fuel rods. A permanent repository in Yucca Mountain in Nevada is still in development.

Environmental groups such as the Natural Resources Defense Council, a member of the U.S. Climate Partnership, continue to resist governmental policies that encourage development of nuclear power, which could complicate efforts to pass a greenhouse gas emissions cap.

But Whitman said she has noticed a shift here, too. More environmental groups, while not yet accepting of nuclear power, seem more amenable to compromise.

“They are willing to talk. They haven’t been in the past,” she said.