Corning Incorporated announced Tuesday it would eliminate up to 4,900 jobs to cut costs as it posted weaker-than-expected quarterly results and outlook due to a significant decline in demand for glass for televisions and computer monitors. Corning said it would cut 3,500 employees, or about 13 percent of its workforce, by the end of the year and said more layoffs could be necessary. The 150-year-old glassmaker also said it is slashing more than 1,400 temporary workers. Corning's shares fell more than 7 percent after the company, whose glass is used for flat-panel video displays and fiber-optic cables, said fourth-quarter profit fell to $249 million from $768 million a year ago. “We experienced a significant momentum shift in many of our core businesses in the fourth quarter as the recession took hold,” chief executive Wendell Weeks said in a statement. “As a result, we are adjusting our operations to reflect anticipated lower sales in 2009.” The specialty glass maker said it expects “a slow start to 2009,” with first-quarter video-display volume down 20 to 25 percent as the supply chain continues to reduce inventory. As the global economy has deteriorated, demand from manufacturers for liquid crystal displays in flat-panel televisions and computer monitors has decreased. The slowdown has been particularly sharp among companies that assemble televisions and from Corning's customers in Taiwan.