US Energy Secretary Steven Chu pledged Tuesday the administration would pursue "clean coal" technology, even as it focuses research on alternatives such as wind and solar.

The US coal industry and lawmakers from coal-mining states have mounted an aggressive campaign to promote investment in cleaner coal as President Barack Obama's administration takes tougher action on the environment.

But many environmentalists say that clean coal methods -- such as capturing and storing carbon emissions -- are unproven and drain resources from finding real ways to combat global warming.

Chu, asked during testimony at the Senate Appropriations Committee whether the administration was committed to researching clean coal, replied: "Yes."

Presenting the 2010 budget requests, Chu acknowledged the administration's views had changed after Congress made clean coal a priority in its 787 billion-dollar stimulus package.

"Certainly if it were not for the Recovery Act funds, you would have seen a different budget," Chu said.

Chu, a Nobel Prize-winning physicist, said before taking office that his "worst nightmare" was for the world to continue using coal at its current pace -- comments seized upon by global warming skeptics.

Chu renewed Obama's promise to step up research in key areas such as solar power, which would enjoy an 82 percent funding boost under the budget.

"To solve the energy problem, the Department of Energy must strive to be the modern version of Bell Laboratories," Chu said, referring to the center whose research led to breakthroughs such as cellphones and solar cells.

"A collaborative effort is our best hope of achieving priority goals such as making solar energy costs competitive with fossil fuels or developing new building designs that use dramatically less energy," Chu said.

Chu spoke shortly before Obama unveiled the first-ever US nationwide standards to combat greenhouse gas pollution from automobiles.