RJR Nabisco Inc. has approached its banks about easing the terms on $6 billion in loans, according to sources with knowledge of the talks. RJR is arguing that relaxed terms are justified because it has dramatically shored up its balance sheet since undergoing a $25-billion leveraged buyout two years ago, the sources said. The giant tobacco and food company has reduced its outstanding debt by $7 billion and raised $2.7 billion in equity since last summer. The New York-based company wants its lenders to relax conditions, including that it use excess cash flow to prepay bank debt. RJR reportedly wants to be free to use those funds for product investment or to retire more costly junk bonds. The company also wants to reduce the interest rate on a $2.25-billion term loan.