Yad Vashem, Israel’s official Holocaust memorial and museum, is embroiled in controversy after attempting to intervene in planned sanctions against Israeli Russian billionaire Roman Abramovich, owner of the Chelsea Premier League soccer team and a longtime supporter of Russian President Vladimir Putin.

In a letter to U.S. Ambassador Tom Nides, Yad Vashem, together with the country’s chief Ashkenazi Rabbi David Lau and Sheba Medical Center Director Yitshak Kreiss, asked that the United States not sanction Abramovich, a major donor to the memorial and other Jewish causes. They said that sanctioning him would cause harm to Jewish institutions that rely on him for donations, said Yad Vashem Chairman Dani Dayan. He said Abramovich was the museum’s second-largest private donor, after the late Sheldon Adelson and his widow, Miriam.

“Mr. Abramovich has contributed to worthy causes for more than a decade,” Dayan said. “As far as I know, Mr. Abramovich doesn’t have any links to Mr. Putin.”

Israel has walked a diplomatic tightrope in its response to the war in Ukraine. Israeli officials have said they support Ukraine, a country with the only other Jewish head of state in the world and what they call a liberal democratic ally. But they are wary of provoking Russia, which backs the Syrian regime on Israel’s northern border and has unofficially allowed Israel to carry out strikes against efforts to transfer weapons to Hezbollah, an Iranian-backed Shiite group, in Lebanon.

Jerusalem has refused several requests for help from Ukrainian President Volodymyr Zelensky, including for the transfer of military equipment.

Israel’s ambiguity about the Ukraine invasion was on display Wednesday, when Israeli and German leaders gathered at the Yad Vashem memorial vowing to prevent the loss of life in Ukraine — without publicly mentioning Russia.