Continental Resources (CLR) CEO Harold Hamm warned on Wednesday that if crude prices fell below $40 per barrel many U.S. producers would stop drilling.

On Wednesday, U.S. crude traded at about $44 a barrel.

"This price ... is not sustainable," Hamm said on  CNBC's "Squawk Box." "It needs to be north of $50 for sure to be sustainable in the world."

A drop in prices into the $30 to $40 per barrel range would force drillers to reduce capital expenditures and cease drilling new wells, rendering the market under supplied.

"While this period of adjustment is going on, drillers don't want to drill themselves into oblivion. Backup, and be prudent and use some discipline," Hamm said.

"That's what we're doing at Continental and there are other CEOs I think that are probably doing the same thing. We don't talk about those things," he added.

What's Hot On TheStreet

The stock market may be overvalued: Now may be the time to pay extra attention to red-hot tech stocks such as Apple (AAPL) and Facebook (FB) . As TheStreet first reported Tuesday afternoon, asset valuations are somewhat "rich" by standard metrics, Federal Reserve Chair Janet Yellen said in London during a conversation about economic issues with British Academy President Lord Nicholas Stern. Yellen's comments on equity valuation and bank strength closely mirrored Fed Vice Chairman Stanley Fischer's from an IMF event held earlier in the day.

The iPhone has changed how you make money: TheStreet's Scott Gamm is out with a piece that will really get you thinking. Apple's iPhone will turn 10 years old on Thursday. The device not only turned Apple into one of the world's most valuable companies, helping to boost its stock price more than 700%, it also changed the way we invest and trade stocks Gamm points out.

In fact, the original iPhone -- and the current versions -- have an internal stocks app, allowing users to check the broader market indexes and individual stock prices. Having this in your pocket was a big deal 10 years ago.

"I think it's actually made the life for a typical investor much easier," Angelo Zino, an analyst with CFRA Research, told TheStreet. "I think they've been able to tap news flows much quicker."

Apple, Walgreens Boots Alliance and Facebook are holdings in Jim Cramer's Action Alerts PLUS Charitable Trust Portfolio. Want to be alerted before Cramer buys or sells AAPL, WBA and FB? Learn more now.

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