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* Facebook, Twitter down ahead of Congress appearance
* Deadline for consultations on U.S.-China tariffs looms
* Trade-sensitive Caterpillar, Boeing drop premarket
* Halliburton down on Q3 warnings, weighs on Schlumberger
* Futures down: Dow 0.38 pct, S&P 0.29 pct, Nasdaq 0.35 pct (Adds comments, updates prices)
Sept 5 (Reuters) - U.S. stocks were set to open lower on Wednesday, as investors weighed the likelihood of President Donald Trump going through with plans to slap a fresh round of U.S. tariffs on Chinese goods right after a public comment period ends on Thursday.
Shares of Facebook were down 0.3 percent in premarket trading, while Twitter dropped 0.5 percent as their top executives face the U.S. Congress over what lawmakers see as a failure to combat continuing foreign efforts to influence U.S. politics.
Snapchat-parent Snap Inc was off 0.3 percent ahead of a testimony by Facebook Chief Operating Officer Sheryl Sandberg and Twitter Chief Executive Officer Jack Dorsey from 9:30 a.m. ET (1330 GMT).
"We are definitely going to see a negative tilt today with the big social media leaders appearing in front of Congress," said Scott Brown, chief economist at Raymond James in St. Petersburg, Florida.
"There may be a little bit of nervousness around this, although nothing contributing to a major market move."
U.S. trade deficit rose to a five-month high in July as exports of soybeans and civilian aircraft declined and imports hit a record high, data from the Commerce Department showed, suggesting that trade could be a drag on economic growth in the third quarter.
Trade-sensitive companies Caterpillar and Boeing were down 0.5 percent and 0.7 percent.
The trade data comes as consultations on a U.S. proposal to impose tariffs on $200 billion more in Chinese imports ends on Sept. 6, with Trump ready to impose these tariffs as soon as the comment period ends, according to Bloomberg.
The United States and Canada will also resume talks to settle differences on revamping the North American Free Trade Agreement (NAFTA), despite Trump's threats to continue trade deals with just Mexico in a bilateral agreement.
"There's still a cloud hanging over the market about whether we are actually going to see these tariffs take effect by the end of this week and continued concerns about the NAFTA deal," Brown added.
At 8:39 a.m. ET, Dow e-minis were down 99 points, or 0.38 percent. S&P 500 e-minis were down 8.5 points, or 0.29 percent and Nasdaq 100 e-minis were down 26.5 points, or 0.35 percent.
Energy stocks could come under pressure with crude oil prices down over 1 percent as a tropical storm hitting the U.S. Gulf coast weakened and moved away from oil-producing areas, easing supply concerns.
Halliburton dropped 2 percent after the oilfield services provider said it expects moderating oil and gas activity in North America and a slower-than-expected ramp up of new contracts in the Middle East to hurt third-quarter results.
Shares of rival Schlumberger fell 1.3 percent on the news.
General Electric, whose oilfield services arm is Baker Hughes, was down 1.7 percent. Brokerage UBS cut its price target on GE's stock on concerns over the company's power business.
JD.com declined 4.3 percent, down for the second day in a row, after police said the Chinese retailer's chief executive officer was arrested in Minneapolis last week following an allegation of rape. CEO Richard Liu has denied any wrongdoing and was released on Saturday. (Reporting by Shreyashi Sanyal in Bengaluru; Editing by Shounak Dasgupta)