Averting the possibility of a second writers strike, the WGA has reached a tentative deal with CBS covering about 500 news employees.

The pact, announced Wednesday, ends a battle waged for nearly three years, since the April 2005 expiration of the previous contract.

“This has been a long struggle, but our members became mobilized and engaged in a way they have never been before,” said WGA East exec director Mona Mangan. “This contract truly belongs to them.”

CBS said in a statement, “We are gratified that a tentative agreement has been reached so that CBS and its valued WGA news employees can put this chapter behind us. Our focus throughout the process has been on reaching a fair agreement, and we think this contract is good for both sides.”

Deal comes seven weeks after the CBS News employees repped by the guild gave the WGA a strike authorization with 81% support. The prospect of a picket by the network employees prompted the Democratic National Committee to cancel a presidential debate that had been set for last month in Los Angeles for broadcast on CBS.

Mangan told Daily Variety that for the guild, there were two key issues requiring resolution in the final round of talks: CBS had to drop its demand to create a two-tiered work force that would have provided lower salary increases for local radio employees and back off its demand for the right to assign current WGA responsibilities at KNX Radio to non-WGA employees.

Both sides agreed to a 90-day notification and bargaining period should CBS decide to consolidate operations and agreed that no changes to the contract may be imposed during that period.

The two key initiatives in reaching a deal, according to Mangan, were involving newsroom employees in the contract campaign and lobbying efforts with Congress on the issue of news quality.

The WGA-CBS agreement covers newswriters, editors, desk assistants, production assistants, graphic artists, promotion writers and researchers in New York, Washington, Chicago and Los Angeles.

The WGA said the agreement has been approved unanimously by the WGA-CBS negotiating committee. It must still be ratified by membership vote. If ratified, the new contract will run until April 1, 2010.

WGA-repped CBS News employees will receive a 3.5% raise upon ratification of the contract and again in 2009. The WGA also said that most regularly scheduled employees who worked 200 days or more in 2007 and did not receive wage increases during the negotiations will receive an additional $3,700 payment, while employees who worked shorter schedules will receive pro-rated payments.

“This has been a difficult process,” said WGA East prexy Michael Winship. “We are pleased that it has resulted in an agreement that will protect our members at CBS News and insure that they will continue to bring their exceptional skills, creativity and know-how to the production of quality broadcast journalism.”

WGA West prexy Patric Verrone asked that CBS — a key member of the Alliance of Motion Picture & Television Producers — return to the table to resume the stalled film-TV contract talks. Those negotiations collapsed Dec. 7 after the AMPTP demanded that the WGA remove six proposals from the table.

“This is good news for newswriters and I congratulate them. After months without negotiations, once bargaining resumed, we were able to reach an agreement quickly,” Verrone said. “We ask CBS to come back to the table with the will to make a deal with striking film and television writers.”