Hillary Clinton is taking a strong line against the “BDS” movement that calls for boycotts, divestment and sanctions against Israel.

In a letter to major Democratic donor Haim Saban that was released publicly, Clinton asks for advice on how to fight the BDS movement, which she argues is seeking to “isolate and delegitimize Israel.”

“BDS seeks to punish Israel and dictate how the Israelis and Palestinians should resolve the core issues of their conflict. This is not the path to peace,” writes Clinton, “From Congress and state legislatures to boardrooms and classrooms, we need to engage all people of good faith, regardless of their political persuasion or their views on policy specifics, in explaining why the BDS campaign is counterproductive to the pursuit of peace and harmful to Israelis and Palestinians alike.”

Clinton’s noted ended with a handwritten note to Saban, which said “Look forward to working with you on this.”

Israel’s government and its supporters have grown increasingly worried about the BDS movement, which was inspired by the effort to isolate South Africa’s Apartheid-era government.

The BDS movement calls on boycotts, divestment and sanctions against Israel and Israeli products in order to compel the country to make certain concessions, including allowing Palestinians to return to land they lost either during the creation of Israel’s borders or during subsequent wars.

Several churches in recent weeks have effectively voted on whether to join the campaign. The Episcopal Church USA voted against doing so, while the United Church of Christ general assembly voted to divest funds at its synod in Cleveland.

Saban, an Egyptian Jew who spent part of his childhood in Israel, has regularly supported calls against the BDS movement. He and major Republican donor Sheldon Adelson have both pledged millions of dollars to push back against BDS efforts on college campuses, according to the Israeli newspaper “Haaretz.”

In her letter to Saban, who has donated $2 million to the pro-Clinton Priorities USA PAC, Clinton shot down comparisons of Israel and Apartheid-era South Africa.

“Israel is a vibrant democracy in a region dominated by autocracy, and it faces existential threats to its survival,” she writes.

“Particularly at a time when anti-Semitism is on the rise across the world—especially in Europe—we need to repudiate forceful efforts to malign and undermine Israel and the Jewish people.”

The Democratic frontrunner has long touted her support of Israel as a senator and secretary of State, a key issue in the American political debate. Her letter also stressed her support for a two-state solution.

A number of Republican candidates regularly reaffirm their commitment to Israel, including Sen. Ted Cruz’s (R-Texas) most recent call to withdraw from the United Nations Human Rights Commission over its vote to condemn Israel over the 2014 conflict with Palestinians.