News Corp chairman and chief executive Rupert Murdoch has said that a plan to begin charging readers of his newspapers online may be delayed.

Murdoch had previously outlined plans to erect pay walls around his vast newspaper empire by the end of News Corp's current fiscal year in June but he indicated that was now unlikely.

"We are working all very, very hard at this but I wouldn't promise that we're going to meet that date," he told reporters in a conference call after releasing News Corp's first-quarter results.

Asked what was causing the delay, he said: "Everything."

"It's a work in progress and there's a huge amount of work going on not just with our sites but with other people," Murdoch said.

The Wall Street Journal is currently the only newspaper in the News Corp group to charge readers for access to all of its content. Other News Corp properties include The Australian, the New York Post and The Times of London.

A slump in newspaper revenue was offset in the first quarter by strong results from News Corp's movie, cable television and book publishing divisions as the company posted an 11 percent rise in quarterly net profit.