Teamsters said this week that unless contract negotiations improve, they plan to strike Monday against Lane Construction Corp. At issue are benefit increases Lane proposed for a three-year contract with approximately 70 of its unionized truck drivers in Maine, Teamsters Local 340 President James Carson said Thursday. Lane is offering $2.25 an hour in total benefit increases over the three-year period, but the union wants increases worth $2.75, he said. Carson said the union is reluctant to strike over a 50-cent difference but that the drivers already have rejected the company’s offer three times. Attempts Friday to contact officials with Lane Construction were unsuccessful. Lane, which has its national headquarters in Meriden, Conn., has operations in 15 eastern states and the District of Columbia, according to the company’s Web site. During peak construction season, it employs 4,500 people. The company owns and operates plants in 11 municipalities in Maine. Its local offices are on Odlin Road in Bangor.