US health regulators have questions about the data submitted by tobacco maker Swedish Match in its bid to become the first company to market a smokeless tobacco product as less harmful than cigarettes.

US Food and Drug Administration scientists say they have concerns about how the company studied its snus tobacco product and its proposal to modify the cancer warning on the packaging.

Snus are teabag-like pouches or loose tobacco that users stick between their cheek and gum to absorb nicotine. They are popular in Scandinavian countries and are part of a growing smokeless tobacco market in the US.