Spain's Rafa Nadal returns the ball to Germany's Alexander Zverev during their 2021 ATP Tour Madrid Open tennis tournament singles quarter-final match at the Caja Magica in Madrid on May 7, 2021. (GABRIEL BOUYS / AFP)

Rafa Nadal has raised doubts about his participation in this year's Tokyo Olympics amid the COVID-19 pandemic, saying on Tuesday that he has to be flexible and cannot give a clear answer until he organises his schedule for the year.

Rafa Nadal said that he is yet to firm up his plans on travelling to Tokyo

Japan has extended a state of emergency in Tokyo and three other areas until the end of May as the country battles a surge in COVID-19 cases, raising new questions about whether the rescheduled July 23-Aug 8 Games should go ahead.

Nadal, who won a singles gold in Beijing 2008 and added a doubles title in Rio de Janeiro eight years later partnering Marc Lopez, said that he is yet to firm up his plans on travelling to Tokyo.

"I don't know yet. Honestly I can't give you a clear answer because I don't know. I don't know my calendar," Nadal told a news conference at the Rome Masters.

"In a normal world I'll never think about missing Olympics. There's no doubt about that. Everybody knows how important it has been for me to always play in the Olympics.

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"Under these circumstances, I don't know. Let's see what's going on in the next couple of months. I need to organise my schedule... In a normal year, I know my schedule almost 100 percent from Jan 1 until the end of the season."

Japan's top-ranked men's and women's players - Kei Nishikori and Naomi Osaka - have raised concerns about staging the Games amid the pandemic.

"This year is a bit different, no? We need to be flexible. We need to adapt about things that are happening," Nadal said.

The 20-times Grand Slam champion, who was beaten in straight sets by Alexander Zverev in last week's Madrid Open, opens his Rome Masters campaign against local favourite Jannik Sinner on Wednesday.

"... Tomorrow is going to be a tough start, one of the toughest possible against Sinner," Nadal said.