Powell gives Bolt and Blake food for thought in semis

Asafa Powell (L) takes a break after the men's 100 meters quarters-final heats at the Jamaican Olympic trials in Kingston city June 28, 2012.

KINGSTON, Jamaica (Reuters) - Asafa Powell clocked the fastest time in the 100 metres semi-finals at the Jamaican Olympic trials on Friday to issue a warning to Usain Bolt and Yohan Blake that he remains a force to be reckoned with.

The former world record holder eased home in a time of 9.92 seconds, looking over his shoulders at Nesta Carter (9.95) and world champion Blake (9.96) as he crossed the line.

Bolt did not display his best form but still won his heat with an ordinary clocking of 10.01.

The triple Olympic champion and world record holder was slow out of the blocks but took the lead by the midway point and toyed with the field over the closing metres to nose out Michael Frater (10.02) to set up a tantalising final later on Friday.

The women's 100m final will be every bit as intriguing.

Beijing Olympic champion Shelly-Ann Fraser-Pryce easily captured her heat, crossing the line unchallenged in a time of 11.02.

Kerron Stewart, who was part of a Jamaican sweep of the 100m podium in Beijing, led the way in the second heat in 11.04, while Veronica Campbell-Brown, a double gold medalist in the 200m, won her heat in 11.03.

(Editing by John O'Brien)