Primus Telecom ( PRTL) plunged 53% Friday after swinging to a second-quarter loss and warning of flat third-quarter sales. The company blamed the industrywide price war for its troubles and said it would push to roll out more integrated services in an effort to defend its turf. But the accelerated spending plan will hurt profits in coming periods. For the second quarter ended June 30, the McLean, Va., provider of Internet and long-distance telecom service posted a loss of $14.9 million, or 17 cents a share. That reverses the year-ago profit of $18.7 million, or 21 cents a share. Revenue rose 4% from a year earlier to $331.6 million. The numbers fell far short of Wall Street's expectations. Analysts surveyed by Thomson First Call had forecast earnings of 10 cents a share on revenue of $348 million. "It is clear that our revenue growth and profitability have been strongly challenged by a changing industry environment throughout the first half of this year," said CEO K. Paul Singh. "During the first quarter we experienced pricing pressure on our core long-distance and dial-up Internet service provider (ISP) products. In the second quarter, this competitive challenge became more intense when major incumbent carriers in our markets used long-distance offerings as a 'loss leader' to encourage customers to subscribe to their bundled local, cellular and broadband services." Primus dropped $1.77 to $1.58.