American government scientists reportedly have achieved what is being described as the Holy Grail of energy research by successfully producing excess energy in a fusion reaction for the first time.

According to a Sunday report in London’s Financial Times, the research at Lawrence Livermore National Laboratory in California could pave the wave for unlimited supplies of cheap, clean energy in the coming decades.

While stations producing fusion energy are still likely decades away, the power source has the potential to dramatically alter the world’s dependence on fossil fuels that many believe is contributing to climate change. Fusion reactions produce no carbon or other greenhouse gases, generate none of the radioactive waste that nuclear energy produces, and only a small amount of hydrogen fuel could power hundreds of homes for decades.

Scientists have been trying unsuccessfully since the 1950s to try and figure out a way to harness the same fusion energy that powers our Sun. While they have succeeded in producing the reaction in the past, the latest breakthrough is the first time they have succeeded in producing more energy than they spent trying to cause it — a so-called net energy gain.

Speaking at a White House event promoting fusion energy in March, Virginia Democratic Congressman Don Beyer, the founder of the bipartisan Fusion Energy Caucus and a member of the House Committee on Science, Space, and Technology, said harvesting the energy that powers hundreds of billions of stars across the galaxies — once the realm of science fiction — is now within man’s grasp.

“Fusion is the Holy Grail of climate change and a decarbonized future,” Mr. Beyer said. “Perhaps even more profoundly, fusion has the potential to lift more citizens of the world out of poverty than any idea since fire.”

According to the report, officials at the U.S. Department of Energy — Energy Secretary Jennifer Granholm and the undersecretary for nuclear security, Jill Hruby, among them — will hold a press conference at the Livermore facility on Tuesday to announce “a major scientific breakthrough,” but have not revealed any further details on the announcement.

Sources told the FT that scientists at the lab used a process that involves bombarding a pellet of hydrogen plasma with the world’s largest laser. In the last weeks, the process generated more energy than is consumed by the laser for the first time. The burst of energy produced was said to be so large and surprising that it broke some of the monitoring equipment at the Livermore labs.