LONDON (AP) — Britain's Paula Radcliffe says her chances of running in the Olympic marathon are "not looking good" because of a foot injury that flared up during training the past month.

The 38-year-old world-record holder in the marathon denied a British newspaper report Sunday that she had withdrawn from the Aug. 5 race. UK Athletics and the British Olympic Association also said they were unaware of any decision by Radcliffe to withdraw.

Radcliffe tweeted: "Not looking good but my heartbreaking news to break!" She added that she won't make a decision until a final training run.

Radcliffe has been slowed by injuries since winning the 2005 world championship. The three-time New York City Marathon winner failed to finish the 2004 Athens marathon and was 23rd in Beijing in 2008.