US pharmacy giant Walgreens has postponed plans to sell do-it-yourself DNA test kits after the government safety watchdog suggested the tests needed regulatory approval, the retail chain said.

The Pathway Genomics Insight Saliva Collection Kit was to have gone on sale on Friday at Walgreens stores across the United States, promoted as an easy way for people to determine their risk from cancer, diabetes, Alzheimer's and other diseases. But the US Food and Drug Administration last week contacted Pathway Genomics to say its test needed regulatory approval before it could be sold over-the-counter.

"In light of the FDA contacting Pathway Genomics about its genetic test kit and anticipated ongoing discussions between the two parties, we've elected not to move forward with offering the Pathway product to our customers until we have further clarity on this matter," Walgreens said in a statement.

Dick Thompson, an FDA spokesman, said the agency was still studying the issue.

"We believe this is a device, and this kind of device needs to be cleared by the FDA," he said.

"We understand... that the company believes it is not a device, so we sent a letter on Monday asking them to explain to us how they came to that conclusion. We haven't had an answer yet," Mr Thompson said.

The Pathway Genomics kit was to have been sold for £20 to £30.

Customers would use the kit to take a saliva sample which they would then send to Pathway Genomics' lab for analysis.

Similar tests have been available for purchase over the internet, but it would be the first time they were sold through retail stores.

Mr Thompson did not rule out FDA approval for the kits but said the government agency first wanted more information about "lots of things in terms of this test.

"How reliable is it? How reproducible are the results, and what do those results mean?" he said, adding that a number of issues would be clarified if the kit went through the usual FDA approval process.