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Ackman: I'm more bullish on stocks than Tepper
Ackman: I'm more bullish on stocks than Tepper · CNBC

Billionaire Bill Ackman said Friday he's more bullish on the stock market than fellow hedge-fund titan David Tepper based on valuations.

"Stocks are pretty cheap," Ackman told CNBC's " Squawk Box ," a day after Tepper said on the show that he's "not as bullish" as he could be on U.S. equities.

"Currency [fluctuations] have been largely reflected in next year's [earnings] estimates," Ackman said.

Read More David Tepper: Good time to take money off the table

Caught up in the stock market turmoil on concerns about China's slowing economy, Ackman's Pershing Square Capital, with $19 billion in assets under management, lost 9.2 percent last month, erasing gains for the year.

"Talk to anyone who knows anything about China [growth], they'll tell you that 7 percent is fiction, 5 percent is probably a fiction, and real growth in China is something like 1 percent to 4 percent," he said.

Last year, the Pershing Square boss was the top-performing hedge fund with a return of more than 40 percent.

But Ackman said he's not sure how the rest of 2015 will shake out.

"We're principally a long-only fund, with the exception of Herbalife (HLF) [short]. We own concentrated positions in companies. We own them for years," he said.

"I can't tell you where any of our stocks are going to be next month. I can't even tell you where they are going to be at the end of the year," he continued. "Mondelez (MDLZ) will be a much more valuable company a year from now than it is today. Two years from now, it's going to be even more valuable."

Last month, the activist investor disclosed a 7.5 percent stake in snack and beverage giant Mondelez, worth about $5.5 billion at the time.

Shortly after that, Warren Buffett told CNBC a deal between Mondelez and Kraft Heinz (KHC) was unlikely in the near term. Mondelez spun off from Kraft Foods in 2012.

Ackman said Friday that Mondelez could be a buyout candidate at some point. "If you had to make a list of companies that Buffett would like to own, Mondelez is certainly on the list," he said.

Hedge funder Nelson Peltz of Trian Partners was named to the Mondelez board last year, after taking a stake.

Asked whether he'd seek a board seat, Ackman was cagey, saying "You never know."

"The company is working hard. And Nelson, I'm sure, is part of it," he continued. "We like things where there are lots of ways to make money. One way to make money here is the company remains a standalone business and gets to its potential and will do very, very well."

"Either the current team will get the business to its potential in a reasonablly rapid fashion or it will be a [takeover] target," he added.