• Mercedes driver Lewis Hamilton of Britain smiles to supporters during the autographs session with fans at the 'Sochi Autodrom' Formula One circuit, in Sochi, Russia, on Thursday, April 28, 2016.  The Russian Formula One Grand Prix will be held on Sunday. (AP Photo/Ivan Sekretarev)

    Hamilton expects tough challenge to make up gap on Rosberg

    SOCHI, Russia (AP) — With the gap widening, Lewis Hamilton faces an increasingly tense Formula One title defense as his Mercedes teammate Nico Rosberg grows more confident by the race.