By Justin Palmer
ROSA KHUTOR, Russia (Reuters) - Former Olympic and world champion sprinter Lauryn Williams showed why she was selected to push the USA-1 sled after just six months in the sport when she propelled Elana Meyers to the halfway lead in women's bobsleigh on Tuesday.
Meyers and Williams, 30, helped by two track record starts, eked out a lead of 0.23 seconds over Canada's 2010 champions Kaillie Humphries and Heather Moyse.
The USA-2 sled of Jamie Greubel and Aja Evans sit in bronze medal position ahead of the final two runs on Wednesday.
Williams, who won the world 100 meters title in 2005, Olympic 100 silver at the 2004 Olympics and 4x100m relay gold at last year's London Games, quit athletics in June.
She is poised to become only the second athlete to win Winter and Summer Olympic gold after compatriot Edward Eagan who took gold in boxing at the Antwerp 1920 Olympic Games and finished first in bobsleigh at the Lake Placid 1932 Winter Games.
The diminutive Williams was lured to bobsleigh by fellow crossover track recruit Lolo Jones, the outspoken hurdler who also made her Olympic debut in the USA-3 sled.
Brakeman Jones and driver Jazmine Fenlator could not match their compatriots' speed and sit 11th and out of medal contention.
Meyers, who won 2010 Olympic bronze with pilot Erin Pac, put her boom or bust build-up behind her with two solid drives at a rain-lashed Sanki Sliding Center.
Quickest in three official training runs, the American also crashed twice, the second occasion necessitating hasty sled repairs after Williams was late in applying the brakes.
(Reporting by Justin Palmer, editing by Toby Davis)