* Futures down: Dow 27 pts, S&P 6.75 pts, Nasdaq 12.75 pts
By Yashaswini Swamynathan
April 18 (Reuters) - U.S. stock index futures were lower on Tuesday as investors weighed a possible delay in tax reforms, while keeping an eye on quarterly earnings and global politics.
* U.S. Treasury Secretary Steven Mnuchin told the Financial Times on Monday that the Trump administration's timetable for tax reform was probably delayed following setbacks in negotiations with Congress over healthcare.
* Mnuchin's statement added to concerns about President Donald Trump's ability to deliver on his promises to cut taxes and simplify regulations - bets on which U.S. stocks have hit record highs since his election.
* A raft of quarterly earnings from corporate heavyweights is expected to keep investors busy. Bank of America shares rose 1.3 percent premarket after the company reported a strong jump in quarterly profit.
* Goldman Sachs, which is scheduled to report results before markets open, was up 0.3 percent.
* Safe-haven bets continued to be in favor as investors remained on the edge ahead of critical presidential elections in France and tensions between the United States and North Korea.
* In an unscheduled statement, British Prime Minister Theresa May called for an early election on June 8 to guarantee political stability as the country negotiates its way out of the European Union.
* Gold prices hovered close to five-month highs, while the dollar dipped.
* Wall Street had closed higher in very thin trading volumes on Monday as investors bought technology and bank stocks.
* Shares of Dow component UnitedHealth rose 2.3 percent to $170.95 premarket after the health insurer reported quarterly revenue and profit that beat analysts' estimates.
* Johnson & Johnson slipped 0.9 percent to $124.60 after the healthcare conglomerate reported quarterly revenue that missed analysts' expectations.
* A report on March building permits is due at 8:30 a.m. ET (1230 GMT), while manufacturing output data for the month is expected at 9:15 a.m. ET.
Futures snapshot at 6:55 a.m. ET:
* Dow e-minis were down 27 points, or 0.13 percent, with 27,231 contracts changing hands.
* S&P 500 e-minis were down 6.75 points, or 0.29 percent, with 149,238 contracts traded.
* Nasdaq 100 e-minis were down 12.75 points, or 0.24 percent, on volume of 26,730 contracts. (Reporting by Yashaswini Swamynathan in Bengaluru; Editing by Anil D'Silva)