The stock market posted a broad loss today, registering little enthusiasm over the latest news on the nation's international trade balance. The Commerce Department reported that the U.S. trade deficit in February shrank to its narrowest reading in more than six years. Imports exceeded exports by $6.49 billion, down from $9.32 billion in January. Analysts said that held out the prospect of stronger-than-expected growth in economic output, and improved profits at many companies with a substantial international business. At the same time, however, the figures touched off fresh worries about the outlook for interest rates. In the credit markets prices of long-term government bonds fell more than $10 for each $1,000 in face value, increasing their yields to the 8.84 percent-8.90 percent range.