Tuesday marked the first day of mediated talks between the film and television writers and representatives for the studios that hire them.
The WGA issued a statement late Tuesday saying "no significant progress" had been made.
Wednesday's planned session would be the last before the WGA's current contract expires.
WGA members have voted to authorize a strike, however, a possible walkout will not be declared until at least after Thursday's membership meeting, the Hollywood Reporter said Wednesday.
It is also possible the WGA and the AMPTP will continue negotiations into next week, the trade paper said.
"Both sides worked on modifications to their proposals, (and) the guild indicated that they were preparing a comprehensive package and would be ready to present it tomorrow," AMPTP president Nick Counter said Tuesday.
"We will not agree to any proposals that impose unreasonable restrictions and unjustified costs," he said. "We will not ignore the challenges of today's economic realities, the shifts in audience taste and viewing habits and the unpredictability of still-evolving technology."

