Hedge fund

Harbinger Capital

said Wednesday it likely will sell its shares in



if its tender offer for the software fails Thursday.

The hedge fund warned shareholders in an open letter that the company may return to "business as usual" once Harbinger is out of the picture.

Harbinger made its last-minute plea for investors

to tender their holdings of the software company at $8.30 per share before the June 21 deadline.

"If stockholders do not tender sufficient shares and the board does not permit the tender to close, we will likely sell our shares in the company due to our lack of confidence in the current board," Harbinger said.

The stock closed up 10 cents, or 1.5%, to $6.92 on Wednesday.

Openwave CEO Robert Vrij made his case in a letter filed Tuesday, explaining "why Openwave's standalone plan is a stronger alternative to the Harbinger proposal for employees and shareholders alike."

"Our plan allows for the customer to receive the benefit of a synergistic multi-product solution," Vrij stated. Harbinger's plan "appears to be focused on messaging and divesting most or all other Openwave lines of business," leaving the company exposed to commoditization.

"I believe the Harbinger plan undervalues our ability to bundle multiple products

and our cross portfolio integration capability," among other factors, Vrij said.

Harbinger said Wednesday that it has never said it intends to sell all other business lines and would not do so.