Aereo, the Internet TV startup facing a showdown with broadcasters before the U.S. Supreme Court, said it is no longer signing up users in its initial New York City market because it has no more antennas to rent out.

The New York-based startup, whose investors include Barry Diller’s IAC, would not disclose how many customers it has in NYC. The service provides about two dozen over-the-air TV channels to multiple devices, delivered via tiny, dime-size antennas that are dedicated to individual subscribers. That setup is a key piece of its legal defense, because Aereo says it’s merely renting access to remote antennas instead of retransmitting broadcast TV.

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“Our team has been working overtime to add more capacity in our existing markets,” Aereo rep Virginia Lam Abrams said. “As soon as additional capacity is added, new consumers will be notified that they can sign up and create an Aereo account.”

Aereo’s halt on sign-ups in the Big Apple was reported by DSLReports.com’s Karl Bode, and confirmed by the company Friday.

Aereo has been sued by major broadcasters, including ABC, CBS, Fox and NBC, which allege the startup is illegally retransmitting their TV signals and are seeking to shut down Aereo. The Supreme Court on Jan. 10 said it would hear the case, ABC Television Stations vs. Aereo, with a decision expected sometime this summer.

In early January, Aereo announced $34 million in third-round funding from IAC, media investor Gordon Crawford and Himalaya Capital Management, as well as existing investors Highland Capital Partners, FirstMark Capital and others. The funding brings New York-based Aereo to about $97 million raised to date.

Currently, Aereo is available in 10 markets — falling well short of its goal of rolling out to 22 U.S. cities in 2013. The company has cited technical and weather-related issues for stalling the deployment, and said it expects to expand to another five markets by the end of the first quarter.