A group of US Senators have sent a letter to the European Union expressing concern over its plan to label products manufactured in West Bank settlements.

The letter, addressed to EU foreign policy chief Federica Mogherini, was signed by both Republicans and Democrats.

“As allies, elected representatives of the American people, and strong supporters of Israel, we urge you not to implement this labeling policy, which appears intended to discourage Europeans from purchasing these products and promote a de-facto boycott of Israel,” wrote Senators Ted Cruz, who is currently in the running for the Republican presidential nominee, and Kristen Gillibrand, a Democrat, who spearheaded the statement.

The bipartisan group of Senators argued that the plan sets “troubling precedent” that “play(s) into the narrative of the Boycott, Divestment, and Sanction (BDS) movement, which is an effort to delegitimize Israel rather than promote a resolution of outstanding issues between Israel and the Palestinians.”

The letter continues, “We are also deeply concerned that enacting this policy would lead to the broader boycott of Israel. For decades, it has been the policy of the United States to oppose economic boycotts by other countries against Israel. In the 1970s, the United States Congress enacted legislation making it illegal for a U.S. company to comply with the Arab League boycott of Israel. This year, Congress has passed Trade Promotion Authority (TPA) legislation requiring the United States to discourage Europe from enacting any politically motivated policies that would boycott, divest from, or sanction Israel when negotiating the Transatlantic Trade and Investment Partnership.”

The Senators also implied that the labeling initiative will lead to problems in advancing negotiations between the US and the EU aiming for a mutual cancelation of customs taxes, which the EU has long tried to push forward.

“Differentiating between products made by Israeli companies,” the letter said, “creates a troubling precedent that could eventually lead to the type of activities that the TPA provisions aim to address.”