The Teamsters union — representing more than 4,000 Hollywood drivers, location managers and scouts, casting directors and animal wranglers — is giving the WGA’s strike plans a major boost with a show of solidarity that could seriously disrupt local production.

The leader of Teamsters Local 399 is advising members that they should honor WGA picket lines as long as they’re acting as individuals. The Writers Guild of America could go on strike as early as Thursday; negotiations resume today at the Alliance of Motion Picture & Television Producers offices.

In a message posted Monday, secretary-treasurer Leo Reed said Local 399 can’t strike, picket or boycott a producer while its contract is in effect and must use its “best efforts” to get employees to perform. But Reed added that those restrictions don’t apply to individuals.

“As for me as an individual, I will not cross any picket line whether it is sanctioned or not because I firmly believe that Teamsters do not cross picket lines,” Reed said in the message.

The move was not unexpected, as the Teamsters are the only Hollywood union with specific language allowing members to honor picket lines without reprisal from employers. Reed noted in the message that if Joint Council 42 of the Teamsters sanctions the WGA strike, the companies have agreed that they will not discipline any employee who refuses to cross.

“Federal law protects you if you choose otherwise,” Reed added. “Remember, I believe that Teamsters do not cross picket lines!”

Approval of a sanction for the WGA strike by Joint Council 42 — parent to 23 Teamster locals in California and Nevada — is expected to be a formality.

It’s unclear how many Teamsters will follow Reed’s suggestion and refuse to cross WGA picket lines, but if many do, film and TV production could be hamstrung due to lack a transportation and location managers. And should casting directors not cross, the ability to make quick decisions on actors would be gummed up.

Strong support for the WGA emerged Sunday from the 300 members of Local 399 who attended a meeting at the Sportsmen’s Lodge in Los Angeles.

In response, AMPTP president Nick Counter sent a letter to Reed and other leaders of the five Basic Crafts unions and reminded them of the “no strike” clause in their contract. The five unions signed a three-year deal this summer with the AMPTP.

“We expect each union to comply with this no-strike obligation and order your members to work,” he added. “It is necessary to send you this reminder because of some misinformation and rumors which have been circulated.”

Reed’s announcement offers a stark contrast with guidance provided to members so far by the Screen Actors Guild and the Directors Guild of America — with both guilds emphasizing that if the WGA strikes, SAG and DGA members have to keep working if they have a contract to do so. SAG urged members to join picket lines but noted that they should do so in their free time.

As for the negotiations, both sides have continually blamed each other for the lack of progress at the bargaining table over the past three months. In his most recent message to members, WGA West president Patric Verrone asserted that the AMPTP plan is to stall the talks until the final hours and then make a lowball offer.

“This sort of brinkmanship will likely be met by fear, confusion and even acrimony,” he added. “All that is natural and expected. Therefore, we must be strong and steadfast in our convictions so that we convey the proper message to our employers, to our allies in the entertainment community, to the industry at large and to each other: That as much as we don’t want a strike, we want a bad contract even less.”

Verrone said the guild is planning a general membership meeting Thursday to provide updates on negotiations and the guild’s options. And he warned members to be skeptical of any info that doesn’t come from the WGA.

“In the days to come, there will be many rumors, lies and even threats that will come your way,” he added. “There is a genuine climate of fear on both sides of this negotiation, and it is only natural that misinformation will spread.

“This used to be limited to word of mouth and the mainstream press but, like much in the 21st century, it has taken on a new form with the Internet. Know that we will not be able to keep up with (much less interfere with or attempt to influence) what is posted on blogs and bulletin boards, but we ask you to be discerning in drawing conclusions from those posts and from any source that is not affiliated with the WGA leadership, including the press.”

The membership meeting has been set for 7 p.m. Thursday at the Los Angeles Convention Center.