THE USA Women's team have been given odds of 10/11 to retain their Olympic 4x400m relay title.

That was before news broke on Friday that Debbie Dunn, who finished fourth at the US trials in June, had withdrawn from the women's mile relay team following a positive test for an anabolic steroid at the Championships.

However, the inclusion of the versatile Allyson Felix, who is expected to run both sprint and mile relays as well as the 100m, and 200m, means that the American side which includes US Champs winner Sanya Richards-Ross, Deedee Trotter, and Francena McCorory should not be to hard-pressed in London.

McCorory, who has a season's best of 50.06, and Richards-Ross, who is the second fastest woman this year with 49.78, were both members of a 4x400m relay team which ran the fastest time this year (3:21.18) at the Penn Relays in April.

With three of the 10 fastest women over 400m this year, Russia would be the team most likely to upset the American parade at odds of 9/5.

However, the eastern Europeans have finished bridesmaid to the USA at the last two Olympic Games.

Jamaica claimed the bronze medal at the last two Olympic Games, but having won a silver medal at the 2011 World Championships in Daegu, South Korea, may be hedging their bets on upping their silverware in London.

Novlene Williams-Mills has bested the US darling Richards-Ross at least once this year and will likely anchor the Jamaica squad. However, she will have to bear much of the responsibility of this team with newcomers Christine Day and Dominique Blake in the line-up and former national champion Rosemarie Whyte and Beijing Games 400m silver medallist Shericka Williams not as well-honed as in previous championships.

The Women's 4x400m relay will be the penultimate relay of the Games as usual, but instead of coming ahead of the Men's mile relay, will be followed by the Men's 4x100m relay, closing the show on August 11.