CBS News writers authorized their union leaders to call a national strike, the Writers Guild of America said Monday, escalating a labor impasse.

About 500 CBS News television and radio writers — who work in New York, Los Angeles, Washington and Chicago — have been working under an expired contract since April 2005.

CBS News, a division of CBS Corp., said the vote was "unfortunate," calling its latest offer "fair and reasonable."

In a prepared statement, the company said it "remains fully prepared, and ready to continue producing the highest quality news programming."

In a vote held last Thursday, the union said 81 percent of the 300 writers who participated gave WGA negotiators the power to call a work stoppage.

"Writers Guild members are sending their CBS bosses an irrefutable message of solidarity: we will do whatever it takes to get what we have earned and deserve," Michael Winship, president of Writers Guild of America East, said in a prepared statement.

Hollywood drama and comedy writers, who are also represented by the WGA, are entering the third week of an unrelated industry strike that has shaken network and cable television, threatening popular shows such as Fox's "24" and sending late-night talk shows, such as Comedy Central's "Daily Show with Jon Stewart," into unplanned reruns.

Movie studios felt the sting this weekend, when production starts were scrapped on two high-profile projects, Sony Corp.'s Ron Howard-directed "Angels & Demons" and United Artists' Oliver Stone-directed drama "Pinkville."

Meanwhile, Broadway stagehands represented by the International Alliance of Theatrical Stage Employees are in the second week of a walkout that has canceled most Broadway productions through the Thanksgiving weekend.

CBS News and the WGA have not been at the negotiating table since January after the union rejected what CBS at the time called its final offer in November 2006.

The employees balked at a wage package that would pay television and network radio workers a higher wage than local radio writers. The union also rejected CBS demands to assign nonunion staff certain writing duties currently reserved for union employees.

CBS argues that declining advertising revenues at local radio stations mandates lower station operating costs, including less robust increases in employee pay.