Belgrade: Croatians Marin Cilic and Borna Coric will join world No.1 Novak Djokovic's tennis tournament to be played across the Balkans from June 13 to July 5, the Serb said on Tuesday.
Their inclusion will complete a formidable field also featuring Alexander Zverev, Dominic Thiem and Grigor Dimitrov, with the first of four legs set to take place in Belgrade on June 13 and 14.
The series will then move to Croatia's coastal resort Zadar, where 2014 US Open winner Cilic and 23-year old Coric will take centre stage in front of their home fans.
"I thank Marin and Borna for joining the tour without asking for any financial compensation," said Djokovic, the winner of 17 Grand Slam titles who went on an 18-0 run at the start of the season before the stoppage caused by the COVID-19 pandemic.
"I have known both of them for a long time, they are great guys and we are good friends, so I am really looking forward to meeting up with them in Zadar.
"Marin is one of the best players ever from this part of the world while Borna has the potential to break into the top five on the men's ATP Tour."
The final two legs of the tour are provisionally to be held in Montenegro and Bosnia, but Djokovic revealed at Monday's news conference in Serbia's capital they might have to be moved if the infrastructure is not completed in time.
Djokovic returned to his hometown Belgrade on Sunday after being stranded in the Spanish resort of Marbella for two months, where he was visiting his younger brother Marko when the pandemic broke out.
All four legs of the tour will feature eight players competing in two pools of four on a round-robin basis, with the winners of each pool advancing to the final.