Tesco, the UK's largest retailer, has opened its first US store in the small city of Hemet, near Los Angeles.
The company plans to open dozens of US stores by the end of the year
The retailer decided to go for a "soft launch" of the store at Hemet prior to opening a further five stores in southern California on Thursday.
Tesco is using "Fresh & Easy" as the name for its US venture and will open more stores by the end of the year,
"We need to have live customers in order to test the systems in the store," said a spokeswoman.
"It is entirely logical to do this ahead of the grand opening on 8 November," she said
Tesco chief executive Terry Leahy has said Fresh & Easy could one day rival the retailer's UK business.
The company plans to invest more than $250m (£120m) in its US business launch.
"Tesco's entry could potentially go down as a genuine turning point in the industry, possibly comparable with Wal-Mart's decision to start opening Supercenters in the 1980s", James Anstead, Citigroup retail analyst, said in a recent note to investors.
Tesco is targeting US grocers such as 7-Eleven and locally-run stores using a chain of convenience stores modelled on the Tesco Express blueprint.
Fresh & Easy stores are 75% smaller than most American supermarkets.
The US market is notoriously tough for UK businesses.
Top retailers Sainsbury's and Marks & Spencer have failed to crack the tastes of the US consumer and both have withdrawn back across the Atlantic.
Nevertheless, Credit Suisse forecast in a report this year that Tesco's US sales could reach $1bn within three years, and corner 2% to 6% of the local market share over five years.