U.S. stock index futures were slightly lower Wednesday morning as investors await the signing of the U.S.-China “phase one” trade deal.At around 1:30 a.m. ET, Dow futures fell 49 points, indicating a negative open of more than 14 points. Futures on the S&P and Nasdaq were also marginally lower.Wednesday will mark a key day in U.S.-China trade relations. Both countries are set to sign a “phase one” trade deal in Washington, D.C. Speaking on Tuesday, Treasury secretary Steven Mnuchin said that tariffs on Chinese goods would remain in place until both countries reach an enforceable “phase two” agreement, according to Reuters. Details of the first deal are yet to be disclosed.Furthermore, investors are monitoring corporate earnings with Bank of America, BlackRock and Goldman Sachs due to report. On Tuesday, J.P. Morgan Chase shares jumped on the back of strong quarterly results.On the data calendar, the New York Empire State Fed survey will be released at 8:30 a.m. ET, along with PPI figures.