WASHINGTON (AP) — Saying global warming poses unprecedented threats to Americans' way of life, four of President Barack Obama's top environmental and energy officials urged the Senate on Tuesday to pass legislation to reduce the pollution linked to the planet's rising temperature.

The heads of the Energy Department, Agriculture Department, Interior Department and Environmental Protection Agency told a Senate panel it should pass a bill similar to one the House narrowly cleared late last month. That legislation would impose the first limits on greenhouse gases, eventually leading to an 80 percent reduction by mid-century by putting a price on each ton of climate-altering pollution.

"We will not fully unleash the potential of the clean energy economy unless this committee, and the Senate, put an upper limit on the emissions of heat-trapping gases that are damaging our environment," Interior Secretary Ken Salazar said in prepared testimony. Salazar acknowledged that another Senate panel has already advanced a bill that would boost the amount of energy generated from renewable sources.

Energy Secretary Steven Chu warned that a projected temperature increase would make the world a much different place, and said the only way to avoid that outcome is by enacting legislation.

"Denial of the climate change problem will not change our destiny; a comprehensive energy and climate bill that caps and then reduces carbon emissions will," Chu said.

The appearance of the three Cabinet secretaries and EPA administrator signals the beginning of the Senate's work on a climate bill. The committee hopes to draft and advance legislation before the August recess, and Senate leaders have said they want to take up the measure this fall, before talks on a new global treaty to reduce heat-trapping gases.