Exclusive: Facebook Launching 'Marketplace,' Allowing Users to Buy and Sell With Neighbors

-- Facebook today will announce the launch of Marketplace, a feature within its app on Android and iPhone smartphones which will allow users to buy and sell goods with others, ABC News has exclusively learned.

The long-rumored feature is a challenge to sites like eBay and Craigslist, and will build on similar group functionality within the social network.

In the coming days, the Marketplace feature will begin appearing to people over 18 years old in the bottom row of icons inside the Facebook app. In the beginning it will be limited to users in the United States, the United Kingdom, Australia and New Zealand, the social media company said.

Opening the marketplace, users will see items listed nearby, but will be able to narrow down by price, category or location, according to a forthcoming blog post obtained by ABC News.

Once a desired item is found, the user can then connect with the seller via private messaging to work out payment and delivery -- details that Facebook says it will not handle.

Selling an item will also be straightforward, according to the company. Users take a photo of the item that is for sale, write a short description and verify the location.

It wasn't immediately clear how long listings will remain active.

The new mobile app feature builds on Sale Groups, which have been a feature on the website since February 2015.

Those groups receive about 450 million visitors each month, Facebook said.

The company said that Marketplace will be rolled out in other countries as well as on the desktop website in the coming months.