Uber, the company that hoped to connect taxi drivers with passengers via a smartphone app, has halted its New York City business after only six weeks, claiming that they faced challenges with NYC transportation unions.

In a blog post on its site, Uber co-founder and CEO Travis Kalanick explained the problems, “Demand far out-stripped supply, making you feel pretty lucky when you got a yellow from your iPhone. We did the best we could to get more yellows on the road but New York’s TLC (Taxi and Limousine Commission) put up obstacles and roadblocks in order to squash the effort around e-hail, which they privately have said is legal under the rules. We’ll bite our tongues and keep our frustration here to ourselves.”

The New York Times has more: “A spokesman for the commission, Allan Fromberg, said there was “simply no truth” to Mr. Kalanick’s statement.”