PARIS -- Roger Federer turned down an invitation to play in a planned exhibition match in Saudi Arabia in December which his rivals Novak Djokovic and Rafael Nadal have committed to play in.

Saudi Arabia is under growing pressure from the international community following the killing of Saudi writer Jamal Khashoggi after he entered Saudi Arabia's consulate in Istanbul on Oct. 2. He was a Washington Post columnist who had written critically of Saudi Arabia's crown prince.

Tennis stars Djokovic and Nadal have expressed doubt as to whether they will play an exhibition match at the King Abdullah Sports City in Jeddah on Dec. 22, but they have not withdrawn. Both players have said the invitations were made at least one year ago.

Asked in Paris on Tuesday if he was also previously invited, Federer said "they contacted me too, yeah."

The Swiss star was then asked why he turned it down.

"I didn't want to play there at that time," the 20-time Grand Slam champion said. "So, for me, it was a very quick decision."

Amnesty International has urged Nadal and Djokovic not to play.

"Of course I'm aware of the situation. But I had a commitment since one year ago to play there. And my team is talking to them, to analyze the things. That's it," Nadal said when asked his position on Sunday. "It's terrible that one journalist lost (his) life. I know something happened very bad inside there. So we are looking about how evolves the situation and I hope the things will clarify as soon as possible."

Djokovic also made it clear that the decision to play was made a long time ago.

"We have the commitment with them for over a year, actually last year when we were discussing this potential matchup," he said. "It was my professional tennis decision to do that. Of course I know, I'm aware of what's happening, and it's sad, of course."

The top-ranked Serb also stopped short of confirming his presence.

"My team right now is in touch with the people in Saudi Arabia as well as Rafa's and of course we are all talking to understand the situation better," the 14-time Grand Slam champion said Sunday. "Because right now we just don't have obviously enough information, and we have to look into that a bit more and then we'll make our decision soon."

He added: "We have to get more information on what's happening so we can make a rational decision whether it's good to go or not."

Turkish President Recep Tayyip Erdogan said the investigation needs to be completed swiftly and that he wants an extradition request for 18 suspects detained in Saudi Arabia to be put on trial in Istanbul. The country is also asking Saudi Arabia to help locate Khashoggi's body, which still has not been found.

Turkey alleges that a hit squad from Saudi Arabia traveled to Istanbul to kill the journalist and then tried to cover it up.