Djokovic, who will turn 37 on Wednesday, joins the likes of three-time major winner Andy Murray and seventh-ranked Casper Ruud at the Swiss clay court event.

"He will enter in the second round, either on Tuesday or Wednesday," a spokesman for the tournament told AFP with the Serb star likely to enjoy a bye in the first round.

Djokovic, the winner of a men's record 24 Grand Slam titles, is enduring a nightmare season by his high standards.

He has yet to reach a final on the tour in 2024 let alone win a title with his best performance being a run to the semi-finals of the Australian Open and Monte Carlo Masters.

He was knocked out of the Rome Open in the third round by unheralded Alejandro Tabilo of Chile last weekend.

Djokovic was also injured at the Italian venue when he was accidentally hit on the head by water bottle while signing autographs.

He had initially laughed off the incident and even arrived at a training session wearing a cycling crash helmet.

However, he then revealed that he had been suffering nausea and dizzy spells.

Djokovic will be chasing his 99th tour-level title at the Swiss tournament.