The International Alliance of Theatrical Stage Employees called on Monday for a strike authorization vote, setting in motion potentially the biggest labor showdown in Hollywood since the last writers’ strike 14 years ago.

Some 60,000 IATSE members could end up walking off the job, most of whom are based in Los Angeles. A strike, if it comes, would lead to a nationwide shutdown of TV and film production, because three of the locals — 600, 700 and 800 — are “national” unions.

“It’s coast to coast,” said Joe Martinez, a special effects specialist in IATSE Local 44, who said he believed a strike is increasingly likely. “They think they got us by the balls. We make the product. If we don’t show up to work, what are they going to sell?”

Local 600, the largest of the locals, represents 9,600 camera operators and cinematographers in the U.S. If they walk out, no one would be able to hold a camera on a set in the U.S. Likewise, post-production nationwide would come to a grinding halt without the 8,600 editors represented by Local 700.

IATSE has never gone on strike before, and a strike authorization vote does not mean that a strike will happen this time. But it does show that IATSE is being more aggressive about issues that have lingered over many past negotiations, including long workdays and lower rates for “new media,” without getting resolved.

IATSE negotiators are seeking greater accommodation for rest breaks and longer turnaround times between production hours. The Alliance of Motion Picture and Television Producers — which represents the major studios, including Netflix and Amazon — has refused to make concessions that would shorten the workday, which would significantly raise the studios’ costs.

The strike authorization vote is expected to begin on Oct. 1, with results announced on Oct. 4. If approved, IATSE International President Matthew D. Loeb would have the power to call a strike if further negotiations fail to produce an agreement.

A resounding “yes” vote would be seen as giving the union’s negotiators greater leverage at the bargaining table. But calling a vote also carries the risk that a “no” vote, or an underwhelming “yes” vote, could undermine the union’s position.

The vote will actually be two votes — one covering the Basic Agreement and one for the Area Standards Agreement. The Basic Agreement covers the 13 IATSE locals based on the “West Coast,” which have about 47,000 members in total.

For each local, 75% of the voting members would have to vote in favor for that union’s delegates to support the authorization. The authorization would be decided by a majority vote of the delegates. There are 444 delegates across the 13 locals, according to a union rep who asked not to be identified, so 223 “yes” votes would be needed for approval.

Another 23 IATSE locals — representing production workers in locations around the country — are covered by the Area Standards Agreement. That deal largely reflects the Basic Agreement and is negotiated in parallel with it. The unions covered by the Area Standards Agreement announced Tuesday that they will hold their own strike authorization vote.

The two agreements do not cover production in Canada or other countries. So, conceivably some U.S. productions might try to move abroad if a strike is called. However, Canadian film workers are represented by IATSE locals, and those workers might be expected not to work on productions that had fled the U.S.

Martinez said that the AMPTP’s latest move, in which it refused to response to the IATSE proposal, was seen as an “insult.”

“I believe that the laws of probability now are in favor of a strike,” he said. “They’re going to have to taste this medicine.”

Updated Wednesday with a precise delegate count, and on Thursday with the announcement from the Area Standards Agreement locals.