The United States government will identify the cause of autism by September this year, U.S. Secretary of Health and Human Services Robert F. Kennedy Jr. said on Thursday.

"At your direction, we are going to know by September. We've launched a massive testing and research effort that's going to involve hundreds of scientists from around the world," Kennedy said at a meeting of President Donald Trump's cabinet.

"By September, we will know what has caused the autism epidemic and we'll be able to eliminate those exposures."

Trump in February ordered the creation of a "Make America Healthy Again" Commission made up of Kennedy and other secretaries to look at everything from the rates of autism and asthma in children to how much medicine is being prescribed to them for ADHD or other conditions.

Autism diagnoses in the United States have increased significantly since 2000, intensifying public concern. Scientists have been researching for decades what genetic or environmental factors might contribute to autism, but the causes of most cases remain unclear.

They say that the major drivers of the increase in U.S. autism rates are an expanded definition that includes more types of behaviors and more widespread awareness and diagnosis.

Kennedy has long promoted a debunked link between vaccines and autism despite scientific evidence to the contrary.