A 21-year-old United States national has been arrested by the Australian Federal Police (AFP) at Sydney Airport for importing three kilograms of cocaine into Australia.

He is scheduled to appear in Sydney Central Local Court today.

Customs and Border Protection officers stopped the man for questioning when he arrived at Sydney International Airport on a flight from Los Angeles on Sunday.

Following an x-ray of the man's suitcase and a positive result from a drug detector dog, officers found a substance concealed in the lining of his suitcase.

Initial testing indicated the substance was cocaine, weighing approximately 3 kilograms and worth an estimated street value of $1.5 million.

The man was referred to the AFP and charged with importing a commercial quantity of a border controlled drug, namely cocaine, contrary to section 307.1 of the Criminal Code Act 1995.

The maximum penalty for this offence is life imprisonment and/or an $825,000 fine.

Further forensic testing will be undertaken to confirm the exact weight and purity of the substance.