By Graham Wood

ATHENS (Reuters) - Greek 100 meters butterfly champion Kristel Vourna has spoken of her “relief and joy” after an unlikely U-turn by the World Swimming Federation (FINA) following an initial blunder which means she can participate in next month's Rio Olympics.

The 24-year-old, who was initially told by FINA two weeks ago that she had qualified for the Games after making the B standard time, was left devastated days later when the ruling body said her invitation was down to an administrative error.

According to FINA regulations, in order for two athletes from the same country to participate in the same event both must have posted A standard times.

This was not the case for Vourna, who was behind compatriot Anna Doundounaki, and FINA retracted her invitation having realized its mistake.

But following discussions between the Greek swimming federation (KOE), the International Olympic Committee (IOC) and FINA, Vourna has been reinstated.

“It’s been a very strange couple of weeks and I’ve been through all kinds of emotions, but now the most strongest ones are relief and joy that I’m going to Rio,” Vourna told Reuters.

“I didn’t expect FINA to change their decision at all. I was really upset and actually more angry than anything else.”

Initial efforts by the Hellenic Olympic Committee (HOC) to reinstate Vourna were rejected by FINA which said there could be no exceptions.

“This time, personally as the head of the Greek federation, I would like to thank both FINA and Cornel Marculescu for their extraordinary action in favor of Vourna,” said Dimitris Diathesopoulos, who is also a member of the FINA committee.

FINA had offered to cover Vourna’s costs to travel to Rio as a spectator.

“That was the worst for me. It was simply embarrassing and an insult to my dream. I didn’t want to go to Rio as a tourist,” she said.

Vourna will now compete in her second Olympics following London 2012.

“I’ve missed a week of training so I have to work hard, but psychologically the whole episode has given me even more motivation to go there and do the best I can,” she said.

(Editing by Ed Osmond)