Goldman Sachs & Co. has been hired by Public Storage Inc. to advise the company on its unsolicited bid to acquire rival Shurgard Storage Centers Inc., the Glendale-based operator of self-storage facilities said Wednesday.

On Aug. 1, Public Storage based went public to make an appeal to shareholders to support its nearly $2.5 billion offer for its rival despite the position of Shurgard, a Seattle-based real estate investment trust, that it is not for sale.

Shurgard’s board of directors rejected Public Storage’s July 8 merger offer that would exchange each share of Shurgard’s common stock for 0.8 shares of Public Storage stock via a July 26 letter. Based on Public Storage’s close on July 29, the last day of trading prior to the announcement, the proposed transaction represented a 14 percent premium to Shurgard’s stock price.

Public Storage said it believes a merger of the two companies would be in the best interests of shareholders, a position Shurgard disputes.

“We are disappointed that Shurgard’s Board continues to refuse to sit down with us to explore the potential of a mutually beneficial transaction, despite the overwhelmingly positive response from shareholders and analysts to our proposal,’ said Ronald L. Havner, Jr., chief executive officer of Public Storage, in a statement Wednesday. “It remains our preference to work cooperatively with Shurgard to effectuate this transaction.”

Public Storage said the firm of Wachtell Lipton Rosen & Katz is serving as legal counsel in connection with the offer.

Public Storage shares closed up 0.4 percent to $65.82 on Wednesday.