Image caption The high cost of print publishing meant rising costs at Newsweek

Newsweek, the 80-year-old US current affairs magazine, is to become an online-only publication.

The last print edition will be on 31 December, reflecting the trend for newspapers and magazines to move online as traditional advertising declines.

Newsweek merged with the internet news group the Daily Beast two years ago.

The Daily Beast's founder, Tina Brown, said its site now had more than 15 million unique visitors a month, a 70% increase on last year.

She said in a statement: "Exiting print is an extremely difficult moment for all of us who love the romance of print and the unique weekly camaraderie of those hectic hours before the close on Friday night.

Analysis In 1933, Newsweek hit the news stands - a weekly magazine covering global events. But much like the world it's reported on over the last 80 years, much has changed in the publishing world too. Not least how consumers get their news. The number of Newsweek subscribers has slumped from more than 3 million at its peak to 1.5 million today. Couple that with falling advertising revenues for traditional print media and it's led Newsweek to ditch its print edition altogether. Newsweek Global, the digital only version, will be available via a subscription. It's a way of tapping into the 70 million consumers who now use tablet computers in the US, a figure that's soared from just 13 million two years ago. But while it's a large market, there are also more competitors, and analysts say standing out in a digital world will be tough.

"But as we head for the 80th anniversary of Newsweek next year, we must sustain the journalism that gives the magazine its purpose - and embrace the all-digital future.

"This decision is not about the quality of the brand or the journalism - that is as powerful as ever. It is about the challenging economics of print publishing and distribution."

Newsweek rose to become the second largest US news weekly magazine, behind Time. But declining circulation and advertising saw it fall into losses.

It was sold by the Washington Post Company to Sidney Harman in August 2010, and was merged with the Daily Beast three months later.

Tina Brown, who became Lady Evans when her husband Harold Evans, the legendary journalist, was knighted, is a former editor of Vanity Fair and The New Yorker.

She teamed up with Barry Diller to launch The Daily Beast in 2008. The website's name comes from the fictional newspaper in Evelyn Waugh's 1938 novel Scoop.

Newsweek's highs and lows