Adds analyst comment, shares

May 8 (Reuters) - Mattel MAT.O investor Southeastern Asset Management has called on CEO Ynon Kreiz to explore strategic options for the toy maker to be taken private or bought out by rival Hasbro HAS.O.

The global asset manager holds about 4%, or $170 million of Mattel's common stock, and has been an investor in the company for more than eight years, it said in an open letter to Kreiz on Thursday.

A deal between Mattel and rival Hasbro was possible at this moment, Southeastern said, as the two companies have been engaged in on-and-off talks for decades.

In the face of weak demand for traditional toys and supply-chain bottlenecks, Mattel has been growing its IP-centered family entertainment business through films like "Masters of the Universe," following the success of the "Barbie" movie.

The company last week posted a bigger adjusted operating loss of $70 million from $8 million a year ago for the three months through March. However, it topped quarterly sales expectations.

"Hasbro has done a better job executing on digital growth than Mattel and therefore has more credibility in this important part of the business," the letter said.

"We believe synergies between the two companies would be material, creating a stronger player in a global industry."

Mattel said it was focused on executing its plans around the IP-forward strategy. Hasbro did not immediately respond to a Reuters request for comment.

"The board regularly reviews the company's strategy, performance, and opportunities to enhance long-term value, and will continue to consider the views expressed in Southeastern's letter," Mattel said in a filing.

Southeastern also said Mattel's business could be better suited to being privately held, while a third option could be large media companies that would value Mattel's IP assets better than the public market.

Interest from a media company was the most strategically sound option, while a Hasbro takeout was unlikely, Jefferies analysts said in a note.

"No immediate change is expected, (investor) activism may cap downside and revive optionality (in the stock)."

Mattel's shares were up 2% on Friday.