Shares of Diebold Inc. plunged last week after United Technologies Corp.'s chairman said chances for an acquisition of the North Canton, Ohio, automated teller machine company have diminished.

The shares received an upgrade following the decline.

George David, United Technologies' chairman, told investors Thursday at an investor conference sponsored by Morgan Stanley that an acquisition is "probably less likely rather than more likely."

In March his company announced in March an offer to buy Diebold for $40 a share, or a premium of 66% over the price at the time. Diebold's board rejected the offer, which it said undervalued the company, though its shares immediately surged to close to $40 and have remained in the mid-to-high $30s since.

The shares fell more than 6% Thursday, to close at $35.22. The decline was Diebold's biggest in eight months. By Friday the shares had dropped an additional 0.62%, to $35.

Diebold has been involved in a long-running accounting audit and still must file financial statements with the Securities and Exchange Commission. Last month it released preliminary second-quarter results, the most comprehensive look at its financial status since it released its earnings for the first quarter of last year.

Several observers said last month that Diebold's fundamentals alone made its stock worth $40, and that rejecting the United Technologies bid had been the right call.

Mr. David said United Technologies would not make an acquisition without examining the books. The Hartford, Conn., conglomerate makes Otis elevators, Pratt & Whitney jet engines, and other industrial products.

Gil Luria, an analyst with Wedbush Morgan Securities, upgraded Diebold's stock Thursday to "buy," from "hold," saying the company's fundamentals justified his previous $40 price target, even without an offer from United Technologies.

The stock decline "is more a reflection of a shifting shareholder base as opposed to a change in Diebold's fundamental value," Mr. Luria wrote in a note.

Mr. Luria raised his price target $1, to $41, because of "increased confidence in 2009 goals" and Diebold's cost-cutting efforts. It said last month that it is on track to achieve its three-year, $100 million cost-cutting goal by yearend.