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Stock futures moved lower on Wednesday, Aug. 23, in a retreat after a big surge a day earlier. 

Dow Jones Industrial Average futures were down 0.27% and S&P 500 futures fell 0.32%, while Nasdaq futures slid 0.32%.

Wall Street shook free of the malaise that characterized the beginning of the week to stride confidently higher on Tuesday, Aug. 22. A return to profit for BHP Billiton Ltd. (BHP) - Get BHP Group Ltd Sponsored ADR Report helped industry peers build gains, while a hawkish speech from Donald Trump set off a rally in defense stocks. The Dow added nearly 200 points in one of its best performances of the summer. 

Markets were also looking ahead to central bank activity at the end of the week. Federal Reserve Chair Janet Yellen and her European counterpart Mario Draghi, European Central Bank president, will speak at the annual Economic Policy Symposium in Jackson Hole, Wyoming, a highly anticipated yearly event that stretches from Thursday, Aug. 24, to Saturday, Aug. 26.

Investors will parse Yellen's language to determine whether September is a go for the Fed to begin unwinding its balance sheet. The central bank previously said that was a move that it would implement "relatively soon" provided the economy expands as expected. Paring the Fed's sizable assets would likely tighten monetary conditions in the same way an interest-rate hike would. Another rate increase isn't expected until December at the earliest.

However, weak inflation trends could delay the Fed's timing on reducing its balance sheet and hiking rates. On top of that, a number of Fed officials have said that even with a series of interest rate hikes forecast over the next 18 months, the long-term federal funds rate will likely remain below historical averages.

European markets were choppy Wednesday with major indexes hovering close to flat and looking to end mixed. The FTSE 100 in London was up 0.02%, the CAC 40 in France dipped 0.04%, and Germany's DAX was flat. 

"It is not always when one calls London session boring, but this morning wasn't fun at all," said Fawad Razaqzada, market analyst at Forex.com, in a note. "It was like watching paint dry. There was minimal movements in stock indices, commodities, bonds and FX markets ... This range-bound and choppy price action has been a dominant theme for much of the summer, at least by the London open standards."

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On the U.S. economic calendar Wednesday: a flash reading on PMI for August, new home sales for July, and weekly data on domestic crude stockpiles from the Energy Information Administration.

The future of the North American Free Trade Agreement looks uncertain after President Donald Trump said he has doubts that a deal can be renegotiated. At a campaign rally on Tuesday evening, Trump told the Arizona crowd, "Personally, I don't think we can make a deal ... I think we'll end up probably terminating NAFTA at some point." Mexico, Canada and the U.S. entered into negotiations this month to tinker with the agreement, a deal that has been in force since 1994. Trump railed against free trade on the campaign trail, arguing that it was decimating the manufacturing sector. 

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Walmart Stores Inc. (WMT) - Get Walmart Inc. Report , under a new partnership with Alphabet Inc.'s (GOOGL) - Get Alphabet Inc. Class A Report Google, will allow shoppers to make purchases through the voice-activated device Google Home, the Google Express app or its website. A Google assistant, which is tantamount to an online personal shopper, will be assigned to each customer to fulfill the order and set it up to be delivered to their homes.

"I think this gives us a look into the future of shopping, yes," Walmart president and CEO of U.S. e-commerce, Marc Lore, told TheStreet in an interview. "I think with the advancements in artificial intelligence voice ordering will get better over time."

The initiative launches on Sept. 1, and will be offered with a free one- to three-day shipping service, depending on the size of the order.

Shares of Walmart rose 0.5% in premarket trading on Wednesday.

Apple Inc. (AAPL) - Get Apple Inc. (AAPL) Report has scrapped the idea of an Apple-branded autonomous vehicle and is instead working on the underlying technology that allows a car to drive itself, the New York Times reported. To that end, the company is developing a self-driving shuttle service that ferries employees from one Apple building to another, said sources.

The shuttle likely will be a commercial vehicle from an automaker and Apple will use it to test the autonomous driving technology that it develops, according to the Times.

Salesforce.com Inc. (CRM) - Get salesforce.com, inc. Report was 1.9% lower in premarket trading even after topping quarterly estimates. Adjusted earnings rose to 33 cents a share from 24 cents a year earlier. Sales surged more than 25% to $2.56 billion. Analysts anticipated earnings of 32 cents a share on $2.52 billion in sales.  

Lowe's Cos. (LOW) - Get Lowe's Companies, Inc. (LOW) Report posted second-quarter adjusted profit of $1.57 a share, 5 cents below estimates, while sales rose 6.8% to $19.5 billion, $30 million less than expected. The stock fell 4.9% in premarket trading. 

American Eagle Outfitters Inc. (AEO) - Get American Eagle Outfitters, Inc. Report surged 10.4% before the bell after quarterly profit and sales came in above forecasts. Net income fell to 12 cents a share from 23 cents a year earlier. Adjusted earnings of 19 cents came in 3 cents higher than expected. Revenue of $844.6 million beat estimates of $824 million. Same-store sales increased 2%, a surprise to analysts looking for a 0.4% fall.  

Alphabet and Apple are holdings in Jim Cramer's Action Alerts PLUS Charitable Trust Portfolio. Want to be alerted before Cramer buys or sells GOOGL and AAPL? Learn more now.

Updated from 7:38 a.m. ET, Aug. 23. 

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