The British five-time Formula 1 champion set fastest time of 1:33.232 hr on his 34th lap around the Circuit of the Americas on brisk, sunny day in Austin late on Friday, reports Efe news.
Monaco's Charles Leclerc (Ferrari) was second, just ahead of Dutchman Max Verstappen (Red Bull), who was the best in FP1.
The second session was interrupted for 10 minutes after Romain Grosjean crashed his Haas into a wall. The French driver emerged unscathed, but the car took a beating.
Germany's Sebastian Vettel (Ferrari) was fourth in FP2, while Hamilton's Finnish teammate, Valtteri Bottas, took the fifth spot, followed in sixth by Thai driver Alex Albon (Red Bull).
Frenchman Pierre Gasly (Toro Rosso) was seventh and Spain's Carlos Sainz (McLaren) improved from 12th in FP1 to eighth.
Lance Stroll of Canada, who drives for Racing Point, finished ninth and Italy's Antonio Giovinazzi (Alfa Romeo) took 10th place.
FP3 and three rounds of qualifying will be held on Saturday afternoon.
The race the 19th of the 21-race 2019 F1 season will take place on Sunday afternoon.
Hamilton will clinch a sixth F1 drivers' title on Sunday unless he fails to finish in the top eight and Bottas wins the race.
With yet another championship, the 34-year-old would move within one of the record held by German racing legend Michael Schumacher, who won seven drivers' titles between 1994 and 2004.
Hamilton leads the 2019 drivers' standings with 363 points, 74 more than the second-place Bottas.
The driver and his car have been remarkably consistent throughout the year, with Hamilton not having been forced to retire from a single race and only once finishing outside of the top five through 18 races.
After the US stop, the season will conclude with the Brazilian Grand Prix at the Jose Carlos Pace Autodrome in Sao Paulo's Interlagos neighbourhood on November 17 and the Abu Dhabi Grand Prix on December 1.
Mercedes clinched its sixth consecutive constructors' championship at last month's Japanese Grand Prix.
( With inputs from IANS )