"We will soon shed those American clients who are taxable in the United States," bank spokesman Franz Wuerth told ATS news agency confirming reports by several regional papers.
But he added that Raiffeisen had "very few foreign clients and even fewer from America". Only 0.03 percent of its clients would be affected out of a total 3.5 million.
Coop, another retail bank, announced it had stopped doing business with its US clients.
US tax officials have been putting pressure on Swiss banks to release information about clients who are US nationals and who might be evading taxes and the two countries are involved in talks to settle the dispute.
Overall, 11 Swiss or Switzerland-based banks have been targeted including Credit Suisse, Julius Bär, Wegelin, Zürcher Kantonalbank (ZKB), Basler Kantonalbank (BKB), Neue Zürcher Bank, the Swiss subsidiary of HSBC, Liechtensteinische Landesbank (LLB), as well as Israel's Leumi, Hapoalim and Mizrahi banks.
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As part of the ongoing negotiations Finance Minister Eveline Widmer-Schlumpf has authorized Swiss banks to reveal to US authorities the names of their staff working with US clients.
The data transfer to US justice authorities has caused alarm among bankers who fear that they might be arrested on arrival in the United States.