By Justin Palmer

LONDON (Reuters) - Sarah Attar became the first female track and field athlete to represent Saudi Arabia at an Olympics when she competed in the 800 meters heats on Wednesday.

The 19-year-old, who wore a white head cover, a long sleeved green top and black leggings and sported luminous green running spikes, received a generous ovation from a capacity-crowd at the Olympic stadium as she trailed in last of the eight runners.

"It's an incredible experience," Attar, who has dual United States citizenship and is a student at Pepperdine University in Los Angeles, told reporters.

Attar, who clocked two minutes 44.95 seconds - over 43 seconds behind heat winner Janeth Jepkosgei Busienei of Kenya, is the second Saudi woman to compete at the Games following judoka Wojdan Ali Seraj Abdulrahim Shaherkani.

The International Olympic Committee (IOC) had extended a special invitation to Shaherkani and Attar after it pressed Saudi Arabia to end its ban on female participation.

Some conservative Saudis had criticized their countrywomen's participation in London after Saudi Arabia broke with its practice of sending male-only teams to the world's biggest sports event.

(Additional reporting by Neil Maidment; Editing by Mark Meadows; mark.meadows@thomsonreuters.com; Reuters Messaging:; mark.meadows.reuters.com@reuters.net; +44 20 7542 7933; For all the latest; Olympic news go to http://www.reuters.com/london-olympics-2012)