NEW YORK, United States — Time Inc. is selling some magazine titles as the struggling publisher tries to push ahead with an online strategy and move past months of talks about selling the entire company.

The owner of Sports Illustrated and People is looking to sell assets that are “non-core” and “relatively smaller” in its portfolio, chief executive officer Rich Battista said Wednesday on a conference call. He didn’t name the magazines Time may sell.

Battista added that Time was open to joint ventures with other companies and would be interested in an outside investor that could provide capital “for a particular opportunity.”

Last month, Time announced that it was sticking with its online strategy rather than sell itself after months of talks with potential acquirers, including Meredith Corp. and a group including Pamplona Capital Management and Jahm Najafi. Time was said to be holding out for a deal that would have valued the New York-based company at more than $20 a share.

The shares slumped as much as 19 percent to $12.20 on Wednesday. The magazine publisher reported first-quarter revenue of $636 million, missing the $642 million average of analysts’ estimates. Its net loss widened as print advertising sales declined 21 percent. Like other magazines, Time is struggling to transform itself as print advertising revenue dries up and the lion’s share of digital advertising dollars goes to Facebook Inc. and Google.

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Time’s earnings conference call suddenly turned testy as one of its investors demanded more detail about its strategic plan.

“You constantly refer to this strategic plan, but you provide no numbers for the shareholders to basically grasp what this company will look like in two or three years,” said Leon Cooperman, of Omega Advisors Inc., which owns 3.9 percent of the magazine publisher, according to data compiled by Bloomberg.

“I think it’s incumbent upon the company to share with the shareholders, the people that have the money invested, what the strategic plan would yield,” Cooperman said. “Because I’m pretty confident that this company can be sold today at at least $18 a share.”

Cooperman urged the company to hold an analyst day and reveal its strategic plan in more detail. “Then we can make an intelligent decision whether we should agitate for a sale or be patient and give you guys a chance to do your magic,” he said.

Battista replied that Time hired an adviser to cut costs and believes it can reach $1 billion in digital revenue as part of its plan, but did not provide a timeline. “In the future we will provide details on what kind of dollars we think that would yield,” he said.

“We are in a business that’s transforming,” Battista said.

By Gerry Smith; editors: Crayton Harrison and Paul Barbagallo.