WASHINGTON (AP) _ NASA has apologized to congressional leaders for an ''ill-advised and inappropriate'' effort to lobby Congress to block a major cut in the space agency's budget, NASA officials said today.

The agency acknowledged that its office of industry affairs sent a memorandum to contractors Aug. 17 asking help in lobbying Congress to keep its budget intact, despite a federal law banning lobbying with appropriated money.

NASA Administrator James C. Fletcher sent a letter apologizing to several members of the Senate Appropriations Committee.

''This action was ill-advised and inappropriate, and we are requesting the return of all copies outside the agency,'' he said. ''Please accept my apology to you and the members of the subcommittee for this lapse in judgment on NASA's part.''

The lobbying effort was disclosed today by Aviation Week magazine.

NASA spokesman David Garrett said the agency acknowledged the action was improper and has ''taken all steps to remedy this situation.'' He said no disciplinary action was planned against those who issued the letter.

Garrett said the letter to contractors followed a subcommittee action that could lead to a cut of $1 billion from the agency's $9.5 billion budget request for the next fiscal year. NASA said the cut could lead to canceling the space station or other programs.

The magazine said such requests for industry lobbying are frequently made but are not put in writing so that no record exists.