Although it has reached a formal agreement to sell most of its assets to another suitor, Finalco Group Inc. said yesterday it would listen to a last-ditch takeover offer from a Michigan business executive who has been trying to get control of the troubled McLean-based leasing company for nearly a year.

Under a standstill agreement that was reached yesterday with an investment partnership controlled by businessman Harold L. Van Arnem of Birmingham, Mich., Finalco promised to consider a buyout offer from Van Arnem's group.

In return, Van Arnem agreed to end his efforts to unseat Finalco's board and derail Finalco's agreement to sell most of its assets to Western Savings and Loan in Phoenix.

The company said it would decide between the two competing bids by Jan. 16.

Finalco said yesterday that Western has sweetened its bid for the company's assets.

Last month, Finalco signed a letter of intent to sell the assets to Western for roughly $27 million in cash and stock.

Yesterday, the company said it had formally agreed to sell the assets to Western for roughly $29.5 million, or an additional $900,000 in cash and $1.7 million in preferred stock.

The agreement is subject to stockholder approval and endorsement by Finalco's financial adviser, Drexel Burnham Lambert Inc. of New York.

Whether or not the Western deal goes through is contingent on what happens between Van Arnem and Finalco, whose once flourishing business of leasing equipment to Fortune 500 companies has fallen on hard times.

Van Arnem controls roughly 1 percent of Finalco stock and has contracted to buy two more large stakes -- including a 44 percent share owned by former Chairman Jon J. Prager -- which would give him 54 percent of the firm.

Van Arnem has denounced the Western deal, and has vowed to derail it and replace Finalco's board.

Under the standstill agreement announced yesterday, Van Arnem would cease his hostile efforts for now and make an offer for the rest of Finalco's shares before Jan. 16, the day his option to buy Prager's shares expires.

Finalco promised that its board would make a recommendation to shareholders about whether to accept Van Arnem's bid instead of proceeding with the Western transaction.

John Cotton, Finalco's chairman, declined comment yesterday, saying that he was precluded from doing so by terms of the standstill agreement. Van Arnem did not return telephone calls.