United Defense Industries' bank debt traded down to 99 5/8 last week in a $5 million trade, down a meager 1/4 from previous levels. The buyer and seller could not be determined. The company, which has a longstanding business relationship with the U.S. Armed Forces, is considered a safe bet even in a slower economy. "There's consistent demand for the industry, and military spending influences what they do," said a dealer. United Defense, based in Arlington, Va., manufactures combat vehicle training systems. Doug Coffey, spokesman, was unaware of the trading levels, but remarked, "That doesn't really affect us. That's the banks' concern." Buzz Raborn, cfo, declined to comment on trading levels. "We just refinanced, so there's nothing to report right now," he said. The company has an $800 million credit arranged by Deutsche Bank and Lehman Brothers. The deal breaks down into a $200 million revolver and a $500 million term loan "B" and a $100 million term loan "A." This replaces a $725 million credit arranged in 1997 through Lehman, Deutsche Bank and Citicorp.