Steel Partners said Wednesday it will launch a tender offer to acquire all outstanding shares in Bull-Dog Sauce Co.

The U.S. investment fund did not announce when it would launch the bid, but said the offering price will be 1,584 yen, or 20 percent higher than Bull-Dog's closing price of 1,320 yen Monday on the Tokyo Stock Exchange. The stock ended Wednesday's trading at 1,336 yen, unchanged from the previous day.

Steel Partners said in a news release that it notified Bull-Dog of the plan in a letter sent Wednesday.

A spokesperson at the famed Japanese sauce maker would not comment, saying the company had not yet received the letter.