Twelve-time champion Rafael Nadal says the colder weather at a delayed French Open will provide the toughest conditions he has faced in Paris.

"The weather is so, so cold. That makes it difficult for everyone," said Nadal.

"The conditions are a little bit extreme to play an outdoor tournament."

The two-week tournament usually starts in late May and concludes in early June.

It was moved back because of the coronavirus pandemic and will begin in the French capital on Sunday.

"Conditions here are the most difficult conditions for me for many different reasons," Nadal, 34, said on Friday.

"Ball is completely different. Ball is super slow, heavy. It's very cold. Slow conditions. Of course, the preparation has been less than usual."

Romanian Simona Halep, who is the women's top seed and arrives in Paris having won the Italian Open this week, says she feels "good" and "confident" but has also acknowledged the challenges posed by the weather.

"When it's cold, it's a little bit heavier and a little bit different," said the 28-year-old.

"It's a big difference between Rome and here, that's for sure. I feel the cold. I feel like I'm struggling a little bit. But for everybody it's the same."

Nadal is always the favourite - Thiem

Nadal has only played one tournament since the professional tour restarted, winning two matches at the Italian Open before losing to Argentine Diego Schwartzman in the quarter-finals.

The 19-time Grand Slam champion, who is aiming to match Swiss rival Roger Federer's all-time tally of major wins, skipped the recent US Open in New York because of travel and safety concerns.

In his opener at Roland Garros, he will play Belarus' world number 83 Egor Gerasimov, who is making his French Open main-draw debut.

"I am here to fight and to play with the highest intensity possible, to practise with the right attitude, to give me a chance. That's the main goal for me," said Nadal.

Nadal is seeded second behind Serbia's Novak Djokovic and has been put in the same side of the draw of recently crowned US Open champion Dominic Thiem.

Nadal has beaten the 27-year-old Austrian in the past two finals at Roland Garros, but if they meet this year it will be in the semi-finals.

Thiem, who is seeded third, says Nadal is still the man to beat.

"I think he's always going to be the big-time favourite when he's playing, when he's healthy and fit," said Thiem.

"He won the tournament 12 times, which is just incredible. He's by far the best clay-court player ever."