Berlin, Aug 18 (DPA) Usain Bolt shook off some early-morning cobwebs as he strolled into the second of the 200 metres at the world championships Tuesday.

The Jamaican superstar won his heat in 20.70 seconds and disappeared swiftly afterwards, mumbling only 'it is alright' as he set his sight on the second round set for the evening.

American Shawn Crawford led the pack with 20.60 seconds but not even the 2004 Olympic champion and 2008 silver medallist is considered a serious threat for Bolt.

Bolt won Olympic gold in a world record 19.30 seconds last year and Sunday started his Berlin title collection with an awesome 100m world record run in 9.58 seconds.

Bolt, who turns 23 the day after Thursday's 200m final, should be unrivalled as defending champion Tyson Gay of the US withdrew due to a groin injury after getting 100m silver. Gay leads the 200 list with 19.58 seconds to Bolt's 19.59.

United States stars LaShawn Merritt and Jeremy Wariner were untroubled in the 400m heats and home gold medal hope Ariane Friedrich made the women's high jump final along with Croatian holder Blaka Vlasic.

World and Olympic champion Gerd Kanter of Estonia qualified for the discus final and the women's 1,500m favourites also advanced from their heats.

The Olympic champion Merritt won his 400m heat in 45.23 seconds and so did the two-time defending champion Wariner in 45.54. Wariner hopes to rebound in Berlin from his Olympic meltdown on the home stretch.

'It was a great first round ... My body is feeling good,' said Merritt.