Webb had withdrawn from the meet but officials said Thursday the American record holder at the distance had re-entered and would join Mexican record holder Pablo Solares, among others, in trying to end the reign of Willis.
Britain's Mo Farah, the reigning 5,000m and 10,000m European champion, will be favored in the 3,000m, which also includes Ethiopian Dejen Gebremeskel, runner-up to American Bernard Lagat at 5,000m last year at Boston, and three-time US college champion Sam Chelanga.
Last year at Barcelona, Farah became the first 5,000-10,000 European double champion since 1990. He also broke David Moorcroft's 28-year-old British 5,000m record last year with a 12min 57.94sec effort.
American Bershawn Jackson, the 2005 world champion and a 2008 Olympic bronze medalist in the 400m hurdles, will forego defending his 400m crown from last year and race in the 600m this weekend.
World indoor mile champion Kalkidan Gezahegne of Ethiopia will be tested by Canadians Sheila Reid and Carmen Hussar in the women's mile.