The New York Times Co. on Monday started offering on its Web site a tool that enables readers to post articles on Digg, Facebook, and Newsvine.com, an indication that the venerable news organization is embracing online social news sharing.

Links for posting to each of the sites have been added to all free articles on NYTimes.com. The "share" tool, which is listed under the print and e-mail options on each story, won't be available on premium content in the company's TimesSelect site, which includes archives and columnists.

"This new capability extends the Web-based conversation while encouraging new communities of readers to share and discuss a wide range of interests, whether by linking to an article about politics from their home page or adding coverage of world news to their blogs," Vivian Schiller, senior VP and general manager of NYTimes.com, said in a statement.

The New York Times Co., which had revenue of $3.4 billion last year, publishes The New York Times, International Herald Tribune, and The Boston Globe. Rather than offer all content for free on the Web, the company has adopted a halfway approach, where premium content is available through online subscriptions or to subscribers of the company's newspapers.

Digg and Newsvine.com let registered users contribute links to online stories and decide through voting which ones get the highest placement on the sites, which also offer discussion forums. Facebook, a social networking site similar to News Corp.'s MySpace, is particularly popular with college students.

Traditional media companies like The New York Times have struggled to hold on to readers, particularly older teens and young adults, as an increasing amount of news is available for free on the Web. Complicating the problem further is the booming online advertising market, which has siphoned dollars from newspapers and magazines.

The New York Times and other older media companies, however, have been extending their reach on the Web through acquisitions. The Times last year paid $410 million in cash for About.com, which offers expert advice on topics ranging from personal finance and home repair to consumer electronics and geography.