Stock futures were mixed on Tuesday, Sept. 26, on continued geopolitical uncertainty and as investors awaited clarity on tax reform plans to be released Wednesday and Fedspeak that will come out mid-morning. 

Dow Jones Industrial Average futures were down 0.02%, S&P 500 futures fell 0.06%, and Nasdaq futures added 0.2%. 

Concerns over warfare with North Korea increased to begin the week, holding markets underwater during the session on Monday, Sept. 25. North Korean officials have engaged in a war of words in recent weeks: on Monday, North Korean Foreign Minister Ri Yong Ho told reporters that the U.S. had "declared war on our country" and that it had the "right" to shoot down U.S. aircraft even outside of its airspace.

North Korea's bellicose language follows on from U.S. President Donald Trump's series of threats at his U.N. General Assembly address when he said he would destroy the country and called North Korean leader Kim Jong-un "rocket man." Trump has yet to comment on the latest threats. 

Meanwhile, further information on the Trump administration's highly coveted tax reform plans will finally be made public on Wednesday. President Trump will lay out "new details" in a speech on Wednesday, Sept. 27, White House press secretary Sarah Huckabee Sanders told reporters on Monday afternoon.

The Big Six -- a group of officials from the White House and Capitol Hill -- will likely scrap a previous plan to cut the corporate tax rate to 15% and instead aim for a rate between 20% to 23% in final legislation, according to Politico. The Big Six group includes Treasury Secretary Steven Mnuchin, House Speaker Paul Ryan, and Senate Majority Leader Mitch McConnell.

The highlight on Tuesday, however, will be an appearance by Federal Reserve Chair Janet Yellen at the National Association for Business Economics Meeting in Cleveland. Yellen is scheduled to deliver the keynote luncheon address at 11:50 a.m. ET. Cleveland Fed President Loretta Mester will moderate a panel discussion on the global outlook at the same meeting at 9:30 a.m.

Also on the economic calendar on Tuesday: The S&P Corelogic Case-Shiller Home Price Index for July will be released shortly before markets open, and new home sales for August, and consumer confidence for September are scheduled for 10 a.m.

Oil prices took a breather early Tuesday, pulling back from a surge tied to the possibility Turkey might shutter major pipelines. Turkey's President Tayyip Erdogan on Monday said he could close the pipeline running out of the Kurdish region of Northern Iraq in response to a non-binding independence referendum that was held on Monday. The pipeline to the Turkish port of Ceyhan pumps about 500,000 to 600,000 barrels of oil per day and is the main transport route for the Kurdish regions oil exports.

West Texas Intermediate was down 0.5% to $51.96 a barrel on Tuesday. Crude prices hit their highest level since mid-April on Monday. 

Tech stocks moved higher in premarket trading in a recovery from  Monday's selloff. The sector had been under pressure on reports that demand for Apple Inc.'s (AAPL) - Get Report latest iPhone models was far less than anticipated. Apple had already been in selloff mode after its newest Apple Watch model was found to have connectivity issues. 

Nvidia Corp. (NVDA) - Get Report was higher after inking a deal to provide chips to some of China's largest cloud-computing companies. Alibaba Group Holding Ltd. (BABA) - Get Report , Baidu Inc. (BIDU) - Get Report , and Tencent Holdings Ltd. are integrating Nvidia's Volta chips into its data centers, according to a statement.  

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Darden Restaurants Inc. (DRI) - Get Report  fell in premarket trading after posting disappointing same-store sales growth. The parent of Olive Garden earned an adjusted 99 cents a share over its recent quarter, in-line with estimates, while revenue of $1.94 billion nudged past consensus of $1.93 billion. Same-store sales increased 1.7%, below forecasts of 2.1% growth. 

Red Hat Inc. (RHT) - Get Report rose in premarket trading after a better-than-expected second quarter. Net income of 53 cents a share came in far higher than 32 cents a share a year earlier. Adjusted earnings of 77 cents a share bested estimates by a dime. Revenue increased nearly 21% to $723.4 million, higher than consensus of $699.6 million. For the third quarter, the open-source software company anticipates revenue of at least $730 million, higher than $710.5 million estimated. 

Micron Technology Inc. (MU) - Get Report and Nike Inc. (NKE) - Get Report  will report earnings after the bell Tuesday. 

Updated from 7:42 a.m. ET, Tuesday, Sept. 26. 

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