WASHINGTON, June 28 -- The Defense Department intends to invest billions of dollars into research on high-energy lasers, microwave systems and other advanced technologies. The work is designed to counter the spread of "asymmetric" threats to US forces over the past decade, Pentagon officials told Congress. Among perceived unconventional threats, they cited ballistic missiles, possibly tipped with nuclear, chemical or biological weapons; keyboard-launched information operations against US military satellites and terrorism. "We must be conscious of these threats as we foster technology breakthroughs ... to cope with that environment," Edward Aldridge, the Pentagon's chief weapons buyer, told the House Armed Services Research and Development Subcommittee. He did not spell out precisely how many billions would go to defense research and development in President Bush's 2002 budget blueprint, but under a provisional budget plan, the sum was to have risen 8.1 percent to $48.6 billion.