Senators Joseph Lieberman, Connecticut Independent, and John McCain, Arizona Republican, asked the EPA in February to analyze their plan to cut US carbon dioxide emissions by 65 percent below 1990 levels by 2050.

The EPA found that the Climate Stewardship and Innovation Act of 2007 would shave up to 1.6 percent, or US$419 billion, off a baseline forecast for US gross domestic product in 2030 and up to 3.2 percent, or US$1.332 trillion, by 2050.

At a hearing before a subcommittee of the Senate Environment Committee Tuesday, Lieberman noted that "nothing is free," but called the impact "manageable and affordable."

The full Senate could weigh climate change legislation for the first time this fall, Lieberman said.

The Senate Environment Committee must sort through at least five proposals to cut global warming.

Sen. Barbara Boxer of California, the panel's chairman, said she wants members to review all the proposals when they return from their summer recess in September.

The United States is the biggest emitter of carbon dioxide, one of the greenhouse gases blamed for global warming, melting glaciers and rising sea levels.

Lieberman also said the EPA analysis found that his plan would hold US carbon dioxide levels below 500 parts per million by the end of the century, a key level that international scientists say will allay the worst global warming impacts.

The EPA analysis also found that US gasoline prices would rise by 26 cents a gallon in 2030 and 68 cents a gallon by 2050, and electricity and natural gas prices would rise slightly.

Cap-and-trade regimes envisioned in many legislative proposals in Congress would create a multibillion-dollar market for trading emissions credits.

If the McCain-Lieberman bill is enacted, the EPA found the market for credits and offsets would be US$25 billion in 2030 and US$57 billion in 2050.