Rafael Nadal's preparation for a tilt at a record-extending 15th French Open title suffered a further blow when he announced Friday his withdrawal from the ATP Barcelona tournament.

The 36-year-old Spaniard said he had still not recovered full fitness from the hip flexor injury he sustained in the Australian Open in January and which saw him miss this week's Monte Carlo Open.

"I am still not ready and so I continue my preparation process for the return to competition," he tweeted.

The Barcelona tournament starts on Saturday and the French Open on May 28.

Nadal said it hurt him to miss Barcelona.

"Barcelona is a special tournament for me because it is my club by adoption and because playing at home is always a unique feeling," he said.

The 22-time Grand Slam singles champion -- he shares the record with Novak Djokovic -- had originally thought he would be out for up to two months.

He pulled out of hard-court tournaments at Indian Wells and Miami, with his sights set on a return at the start of the clay court season.

His fitness problems have become an increasing issue since he won his 14th French Open crown last year.

He eased to victory against Casper Ruud despite having his troublesome left foot anaesthesised to counter the pain -- he was diagnosed with Müller-Weiss syndrome aged 18.

He subsequently withdrew from his Wimbledon semi-final due to an abdominal injury.

His long absence from the circuit this time round has seen him drop out of the top 10 for the first time since April 2005 -- he is presently ranked 15th.