Ethiopian distance runner Kenenisa Bekele and Croatian high jumper Blanka Vlasic will highlight the Rome Diamond League meeting on June 10, organisers announced.
Bekele, the Olympic and world 5,000 and 10,000 metres champion, is likely to run the shorter distance in Rome.
The 14-meeting Diamond League circuit also confirmed it had signed five new athletes for the series, which begins in Doha on May 14.
Olympic champions Shelly-Ann Fraser of Jamaica (women's 100), Valerie Vili of New Zealand (women's shot put) and Barbora Spotakova of Czech Republic (women's javelin) will be part of the circuit along with US world champion sprinter Allyson Felix and former world javelin winner Tero Pitkamaki of Finland.
The quintet join Bekele, Vlasic, sprinters Usain Bolt, Asafa Powell, Tyson Gay and Sanya Richards-Ross, pole vaulters Yelena Isinbayeva and Steve Hooker and Norwegian javelin thrower Andreas Thorkildsen as ambassadors for the series.