The results of the experiment are still being analyzed, the lab spokesperson added.
In the December 5 experiment, scientists shone a laser on a fuel to fuse two light atoms in a denser environment.
The US Department of Energy later said the fusion resulted in 3.15 megajoules of energy, compared to the laser's 2.05 megajoules.
The fusion reaction, in which atoms fuse together, is the process that enables the Sun to generate energy. For nearly 70 years, scientists have been aiming to replicate this process on Earth to produce clean nuclear energy.
If this technology becomes widespread in the future, it could reduce the need for fossil fuels and contribute to the fight against global warming.
However, scientistsemphasize that this is unlikely to happen in the near future and that we should not give up on reducing carbon emissions with current means.