AUSTIN, Texas -- Mercedes' Lewis Hamilton had the fastest time in an extremely wet final practice session at the United States Grand Prix, with cars sliding and spinning through turns.
Heavy rain has pounded the Circuit of the Americas for two days. Friday afternoon's practice was cancelled and drivers were allowed to use only full wet tires Saturday morning. Hamilton was well back before running through a lap of 1 minute, 59.517 seconds.
More heavy rain was expected, raising questions about afternoon qualifying. If officials are forced to set the starting grid with the practice times, Hamilton would earn pole position for Sunday's race as he seeks to win his second consecutive world title and third overall. Sahara Force India's Nico Hulkenberg would be second.
Ferrari's Sebastian Vettel had the second-fastest lap of the session, but wouldn't start there Sunday. Ferrari has been hit with a 10-spot penalty for installing its fifth engine of the season earlier this week.
With an eye on the afternoon weather radar, the teams clearly treated the practice session as a possible qualifier and kept their drivers on the track for long stretches to log laps.
"No complaining. Safe enough to run," Red Bull's Daniel Ricciardo radioed to his garage early in the session.
But the rain kept coming and the cars kept sliding off the track, Hamilton included. Several times he slid through corners or had to take his car wide off course.
"The conditions are quite hard. Keep spinning," Vettel told his crew after one spin through a turn left his car facing backward when it came to a full stop.
Hamilton, who has won twice at the Circuit of the Americas, can clinch the world title if he outscores Vettel by nine points Sunday and his Mercedes teammate Nico Rosberg by two.
Hamilton is also chasing his 10th win of the season, which would make him the first Formula One driver to win 10 or more races in consecutive seasons.
