The service was launched two years ago and competes with Google's AMP.
Facebook will test limiting the number of published news stories that can be read for free on its Instant Articles platform for premium publishers, according to media reports.
The leading social network has become a major source of news for people, triggering complaints by publishers that they lose control and revenue when their stories are shared free at Facebook.
A paywall is under construction in Facebook's Instant Articles section where the social network has agreements with select outlets to publish directly to the platform, according to a story initially published online at TheStreet
The service was launched two years ago and competes with Google's AMP that also optimizes content from select media for mobile web browsing.
Facebook head of news partnerships Campbell Brown said at a digital publishing conference in New York on Tuesday that the social network is responding to publishers' concerns with the move, TheStreet reported.
Facebook in October will begin testing a feature that limits to 10 the number of stories that can be accessed in its "Instant Articles" section and guides readers to publisher home pages to consider buying subscriptions, according to media reports.
California-based Facebook did not respond to an AFP request for comment.
Instant Articles aggregates published stories and quickly loads mobile pages to cater to smartphone or tablet users.
"One of the things we heard in our initial meetings from many newspapers and digital publishers is that 'we want a subscription product -- we want to be able to see a paywall in Facebook," TheStreet quoted Brown as saying at the conference.
"And that is something we're doing now."