"We have conversations with Congress to let them know where we are. And we have been not shy about saying that we don't support legislation that is currently on the Hill," press secretary Dana Perino said.

"We think that it would be bad for the economy, and that it wouldn't -- ultimately, it wouldn't address the problem."

Perino was referring to a bill sponsored by Republican John Warner and Independent Joe Lieberman that would set a limit on the level of carbon emissions and introduce economic incentives for cutting back on pollutants, a system known as "cap and trade."

Democratic Senate Majority leader Harry Reid has scheduled debate on various proposals for combating climate change in early June, Perino said.

"Our views on -- on especially the Warner-Lieberman bill, are well known. We cannot support it," she said.

"We aren't necessarily against cap and trade proposals," she said. "But cap and trade programs can be very complicated. And what we have seen so far from Congress is not something that we could support."

Asked if the president had his own ideas that might be put forward, Perino said: "There could be something," but gave no further details.

The proposals under consideration in the Senate call for reducing greenhouse gas emissions in manufacturing, electricity and transport sectors by 19 percent below 2005 levels by 2020 and 70 percent by 2050.

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