NSW Police allegedly seized 450 kilograms of the highly addictive stimulant from the 25-year-old Alfords Point man.

Investigation began in May when detectives allegedly found 40 grams of methylamphetamine in a storage unit in Alexandria, Sydney.

Police and Australia's Border Force then tracked two inbound international shipments of the illicit drug from the USA in July and Pakistan in September.

The package arriving from the USA held 2.9 kilograms of meth and the Pakistan shipment contained 1.2 kilograms, police said.

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Investigators allege the man used false identities to receive the drug shipments.

The alleged drug trafficker was arrested on September 26 after "extensive inquiries" and was refused bail to appear at the Downing Centre Local Court on November 21.

He was charged with eight offences including three counts of dealing with identity information to commit an indictable offence and two counts of possessing a commercial quantity of border-controlled drugs.

Anyone with information that may assist investigators is urged to contact Crime Stoppers: 1800 333 000 or https://nsw.crimestoppers.com.au. Information is treated in strict confidence.