The website, 11main.com, which is currently in beta, will feature a wide range of products, including "one-of-a-kind items, not available at mass merchants and other large e-commerce sites," Alibaba said.
The website displayed an "opening soon" message early on Wednesday. "Our shop owners are currently unpacking and getting settled," the site said.
The invitation-only marketplace, which Alibaba said would be "inspired by the local Main Street shopping experience," will offer products in a variety of categories such as fashion and style, home and outdoor, and jewelry and watches.
The announcement comes as Alibaba prepares for a U.S. initial public offering that is expected to raise more than $15 billion - the most since Facebook's IPO in 2012.
The company, founded by Jack Ma, controls 80 percent of all online retail in China, handling about $250 billion in 2013 - more than Amazon and eBay Inc combined.
Reuters reported in February that Alibaba was set to launch a U.S. e-commerce website.