A US magazine trade group said Tuesday it would offer a performance guarantee for print advertising as a way of countering the growth of digital media.

The Association of Magazine Media said it would offer marketers a "money- or space-back guarantee" to show print magazines' ability to connect with consumers.

The group said it was launching the initiative based on research that shows the power of print advertising, saying that magazine marketing helped boost sales better than television or online ads.

The research also showed that print ads were even more effective when used in tandem with marketing in other media, the group said.

"While many industries have sat back and lamented the disruption caused by technology, magazine media leadership has twice now put aside its wildly competitive culture to aggressively lead and transform the marketplace," said Nancy Telliho, interim president and chief executive of the group.

The association represents 175 US magazine media companies with more than 900 titles, and some 30 international publishers.

While magazine readership has held relatively stable in the United States, advertising dollars have been shifted to other media, notably to the Internet, where marketers often can track activity and in some cases online purchases.

The guarantee "is a clear and powerful statement that magazine media provides unique value to advertisers," said Stephen Lacy, chairman of the association's board and chief executive officer of the publishing group Meredith Corporation.

"We are confident in our product, its future, and the unique role that print magazines play in our multi-platform ecosystem to drive ROI (return on investment) and lift advertisers' brand sales."

The guarantee covers advertising for items such as food, beauty products, over-the-counter pharmaceuticals, health, pet care and retail, accounting for some 60 percent of ad dollars spent across media.

To qualify for the guarantee, companies must be selling a product or service that is tracked by one or more syndicated research firms such as Nielsen Homescan or Kantar/IRI. This allows measurement of the return on investment or increases in sales based on money spent on advertising.

The association said some publishers have implemented similar programs with "uniformly positive results."