Roger Federer is the favourite to win the French Open but faces strong competition from nine-time champion Rafael Nadal, according to world number 18 Pablo Carreno Busta.

Federer, 35, claimed his 18th grand slam after beating Nadal in the Australian Open final and is set to duel with the ''The King of Clay'' again at Roland Garros.

While the Swiss has sat out the clay court season, 30-year-old Nadal has dominated on his favoured surface claiming his 10th title at the Monte Carlo Masters and Barcelona Open.

Bookmakers have installed the former world number one as favourite to win a 10th title in Paris in the second major of 2017 which starts on Monday 22 May.

Carreno Busta is among a clutch of players who could threaten Federer and Nadal's dominance, having warmed up for the tournament by beating Gilles Muller to scope the Estoril Open title in Portugal.

The 25-year-old, who has lost all four of his matches against the pair, believes both players to be contenders to win the Coupe des Mousquetaires, with Federer expected to prevail.

"Seeing results in 2017, I would say Roger Federer is the favourite to win (in Paris) even if he doesn't play any tournament before it," he said, according to LiveTennis.it. "We should have a look also at Rafael Nadal, who can do some damage too."

Rafael Nadal and Roger Federer
Nadal and Federer have met in four French Open finals – with the Spaniard prevailing on each occasion Reuters

Defending champion Novak Djokovic will arrive in the French capital seeking to arrest a decline in form which was triggered by him completing the career grand slam when he beat Andy Murray to win last year's title. The Serbian is currently without a coach having parted ways with Marian Vajda, and says he could work unaided at the French Open.

"It's clear that Djokovic is not playing as well as he did in the last years, before he was unstoppable," Carreno Busta added. "Only three players could compete against him. But although they he is a very high level player, it is not easy to keep up that way and players are more and more willing to win."