Amazon is finally making good on the initial promise of its $13.7 billion takeover of Whole Foods Market a year ago: that the combined companies could create an online grocery colossus.

That plan still has a long way to go, but Amazon is launching delivery through its Prime Now service of a selection of Whole Foods products in 24 cities, the company announced Tuesday. The e-tailing giant is also promising that its members will get their deliveries "in as little as an hour," according to a press release from the company.

Locally, the service will be available only in lower Manhattan, Brooklyn and parts of Long Island, but will "expand to additional neighborhoods" during the rest of 2018.

Offerings will include "fresh produce, high quality meat and seafood, everyday staples and other locally sourced items" from the supermarket chain.

The combination of Whole Foods and Amazon could pose a far more potent threat to other online grocers than the company's previous stab at the market, AmazonFresh, ever did. But FreshDirect, which recently opened a vast, new distribution center in the Bronx, remains well positioned to hold onto its lead in New York, according to one supermarket consultant.

"FreshDirect to date has done it far better than anyone else," said Burt Flickinger, managing director of Strategic Resource Group. "The market is already over-served with delivery competitors, as well as newcomers, like Walmart's Jet.com."

Amazon launched the Whole Foods delivery service in Austin, Cincinnati, Dallas and Virginia Beach last February.

"We've been delighted with the customer response to delivery in as little as an hour through Prime Now, and we're excited to bring the service to our customers in Fort Lauderdale, Miami, Palm Beach, Long Island and New York City," said Christina Minardi, Whole Foods Market executive vice president of operations, in a statement.