The prestigious Round Tables food festival, due to open next week at upscale Tel Aviv restaurants, has been dealt a blow with two leading chefs bowing out following pressure from the boycott, divestment and sanctions movement.

Gabrielle Hamilton, chef and owner of the Prune restaurant in New York, was to be hosted by the Coffee Bar chain. Her cancellation follows that by Ana Ros, a world-acclaimed chef from Slovenia.

An open letter by BDS supporters, signed by 90 people from the global food industry, called on chefs to cancel their visits to the festival.

According to the activists, events such as Round Tables are part of a campaign to help the Israeli government normalize its denial of Palestinian rights. They said Israel's Foreign Ministry had invested resources in the food festival with the aim of improving the country's image overseas.

The 90 restaurateurs and chefs who signed the letter marked a three-fold increase over a similar letter last year.

The two chefs who bowed out this year have yet to explain why, though associates of Ros have cited professional disagreements.

Boycott supporters are continuing their efforts to convince other chefs to follow suit. They say another chef, Isa Mazzocchi, who has won an award dubbing her the best chef in Italy this year, has also been dropped from the schedule. She is due to appear at the restaurant Hayarkon 99.

But the festival’s organizers say Mazzocchi is already in Israel and her events are sold out, while the festival’s website still shows her as a participant. She has not canceled or asked that her name be removed from the program despite claims by boycott supporters, the organizers say.

According to the BDS letter, the latest cancellations are part of a wave including American football star Michael Bennett and three other chefs who have canceled their participation at Israeli events over the past two years.

The boycotters' efforts follow successes such as cancellations by musicians scheduled to perform at the Meteor Festival in September. Last week a game by Israel’s handball team was almost canceled after calls for a boycott in Spain.

The letter writers said they hoped that culinary skills would not serve as a cover for what they called apartheid and military rule.

The Round Tables Festival, now celebrating its fourth year, lets local people enjoy the work of some of the world’s leading chefs. For several days famous chefs are invited to cook at Israeli restaurants.

This year the festival is devoted to female chefs, catching the momentum after the rise of the #MeToo movement in the United States and elsewhere. Israel's critics, however, have called this hypocritical in light of the "massacres” they say Israel has committed.

For their part, the festival's organizers said that “the Round Tables Festival is a high-level international festival, placing Israel at the forefront of the culinary world, making a mark locally and around the world. It is therefore exposed to incessant attacks by organizations calling for a boycott of Israel.

"We regret that the newspaper chose to publish a story that repeats the nonsense spouted by the aggressive BDS movement, which tries to spread propaganda any way it can at the expense of artists from around the world, linking its activities to one cancellation or another without checking the facts," the organizers said.

Cancellations are common at such large events, they added.

"The festival's organizers will provide the best service to their customers under any circumstance. If an event is canceled, people will be refunded in full, or an alternative will be offered," the organizers said.

"We’re proud and happy to host thousands of people from around the world over the next two weeks, who are coming to enjoy an exceptional experience. The organizers wish all participants and diners from Israel and abroad another year of exciting culinary experiences.”