Facebook is building a feature that would allow users to subscribe to publishers directly from the mobile app, the Wall Street Journal reports. The feature, long-requested by publishers, is expected to roll out by the end of 2017.

Many details remain up in the air, but discussions have centered around making the feature available only on stories published natively to Facebook through its Instant Articles product. Talks have also focused on how to structure the arrangement, with Facebook leaning toward a metered-payment model, which would allow users to read some articles for free each month before prompting them to pay, three of the people familiar with the matter said.

Another point under discussion is how payments would be processed and whether Facebook would get a cut of the revenue. One model being looked at is to have Facebook take payment information but let publishers keep all the money, some of the people said.

"We're working with partners to understand their business and explore ways we can help them drive more value from Facebook. We are taking the time to deeply understand their different goals and needs," Facebook said in a statement.

The new feature would be a boon to publishers who are increasingly emphasizing digital subscriptions to power revenue growth, including the The Wall Street Journal, the New York Times , the Washington Post and the Financial Times.