SAN FRANCISCO, United States — Shares of Levi Strauss & Co. sank as much as 6.6 percent to the lowest since a March initial public offering after Goldman Sachs issued the first sell rating on the clothing company.

Analyst Alexandra Walvis cut her rating on the denim brand to sell from neutral and trimmed her 12-month price target to $19 to $21. Walvis cited "a more challenged US wholesale environment," not only for Levi, but for retailers Ralph Lauren Corp. and PVH Corp. She downgraded both.

Levi’s better brand growth is well understood by investors, so the company’s increasing valuation compared to peers is “unwarranted,” Walvis told clients in a note.

Earlier this month, Levi’s stock had climbed about 39 percent from its IPO price of $17 before a disappointing earnings report drove shares down.

A slowdown in growth for Levi value brands Signature and Denizen will only add to concerns about the deteriorating wholesale situation, Walvis cautioned.

By Cristin Flanagan; editors: Catherine Larkin and Steven Fromm.