Mansur Mohamed Surur, 60, is accused of involvement in the illegal poaching of more than 35 rhinoceros and over 100 elephants, the US attorney for the Southern District of New York said in a statement.
Surur is one of four men accused of conspiring to smuggle at least 10 tons of elephant ivory and least 190 kilograms (nearly 420 pounds) of rhinoceros horns valued at more than $7 million.
They are accused of conspiring to smuggle the ivory and rhino horn from a variety of African countries to buyers in the US and Southeast Asia between December 2012 and May 2019.
They concealed the animal parts in pieces of art such as African masks and statues, the New York investigators say.
Surur was arrested by Kenyan authorities in Mombasa in July last year and is due to be formally arraigned before a US judge later Monday.
He has also been charged with conspiracy to commit money laundering and heroin distribution. The latter charge can carry a life sentence.
Two of his co-accused, a Liberian and a Guinean, were arrested in 2019, while the fourth remains on the run.
Poaching has caused the population of African elephants to plummet over the past decade, according to the International Union for Conservation of Nature (IUCN).
The slaughter is fueled by a seemingly insatiable demand for rhino horn in Asia, where people pay huge sums for a substance — coveted as a traditional medicine — that is composed mainly of keratin, the same substance as in human nails.