Avemco Corp., a national aviation insurance firm based in Bethesda, has delayed a proposed tender offer for shares of a small Wisconsin automobile insurer and will limit any offer to less than 50 percent of the outstanding shares.

According to documents filed with the Securities and Exchange Commission, Avemco decided that a final decision about whether to proceed with an offer for Classified Financial Corp. stock would be delayed "for a brief period of further study."

Avemco Chairman Arnold Johnson said "recent and previously undisclosed" agreements with certain key officers of Classifed led to the new atmosphere of caution. Under the terms cited by Avemco, three of Classified's officers would reveive "substantial retirement benefits" and could retire voluntarily if the firm is sold.

Johnson said that if such rights were exercised, Avemco could face obligations of more than $1.5 million over a 22-year period if a majority of Classified's stock were acquired.

Avemco has been acquiring Classified's shares for about a year and now owns about 12 1/2 percent of its outstanding stock. On Feb. 9, the Bethesda concern said it planned an offer to buy any or all of Classified's shares at $7 apiece. Classified's board has opposed the bid because the directors deemed the price inadequate, Avemco stated.