Nico Rosberg takes pole in shortened US GP F1 qualifying

Qualifying for the Austin race was delayed until Sunday morning after heavy rain washed out Saturday afternoon's planned track action, but worsening conditions through Sunday morning meant the session had to be suspended after Q2.

Rosberg set the fastest time in that segment, a tenth clear of Mercedes team-mate Lewis Hamilton, who Rosberg must beat in the race if he is to prevent Hamilton clinching a third world championship at this event.

Daniel Ricciardo's Red Bull was fastest of all in Q1, but he ended up third on the grid, over a second slower than the two Mercedes.

His team-mate Daniil Kvyat was fourth fastest, just ahead of Sebastian Vettel, who will receive a 10-place grid penalty for taking a fresh engine this weekend.

Sergio Perez beat Force India team-mate Nico Hulkenberg to the sixth fastest time by just over a tenth, while Kimi Raikkonen (who will also take a grid penalty), Felipe Massa and Max Verstappen rounded out the top 10.

Fernando Alonso's predictions of a possible top-10 position in qualifying almost came true, as the McLaren driver missed out by less than a tenth of a second to Verstappen in Q2.

Several drivers, including reigning world champion Hamilton and 2007 title winner Raikkonen, survived lurid moments at Turn 10 as rain worsened in this segment of qualifying, and Alonso's team-mate Jenson Button suggested over team radio that conditions were bordering on unsafe.

Splashing to 11th place on the grid for Alonso represented McLaren's best qualifying result of the season so far, while the second Williams of Valtteri Bottas was 0.069s slower than Alonso in 12th, Bottas complaining of broken suspension on his FW37.

The second McLaren of Button split the two Lotuses of Romain Grosjean and Pastor Maldonado in completing the top 15.

Carlos Sainz Jr joined the Saubers and Manor-Marussias in failing to escape Q1, after crashing heavily in the early stages of that session.

Sainz lost the rear of his Toro Rosso over the kerb at Turn 3, before crashing hard into the barriers on the outside of Turn 4 and causing the session to be stopped while marshals recovered his broken STR10.

The Spaniard will need permission to start the race from the back of the grid after failing to set a time fast enough to make the 107 per cent cut-off.

After the session resumed, Vettel's Ferrari glanced the barriers following a spin at Turn 10, and the four-time world champion tumbled down the timesheet as others gradually improved their times.

The Saubers tried in vain to dislodge Vettel's Ferrari from 15th spot as Q1 came to a close.

Marcus Ericsson was over a second adrift in the end, while team-mate Nasr was a further 0.9s shy, complaining of "zero rear grip" from his C34.

UNITED STATES GP GRID

*10-place grid penalties for Vettel and Raikkonen