The Dixie Chicks have turned down a multimillion dollar endorsement deal with Coca-Cola Co. because the soft drink giant refuses to sign an interim agreement with striking actors’ unions.

An official with the Screen Actors Guild disclosed that Coca-Cola had offered the country music trio a one-year deal. The Chicks — Emily Erwin, Natalie Maines and Martie Siedel — have sold more than 15 million CDs and had their first headlining tour this summer.

Coca-Cola had no comment on the failed negotiations, but a rep for the Dixie Chicks has confirmed the details. Major corporations have mostly refused to shoot ads under interim deals since the strike began May 1, claiming that the terms sought by SAG and the American Federation of Television & Radio Artists are unreasonable.

Strikers picketed a nonunion Coke shoot last month in Virginia and Maryland.

Singing stars support strike

Earlier in the strike, the Backstreet Boys shot a Burger King spot under an interim agreement, Britney Spears canceled a nonunion Clairol shoot and hip-hop artist Lil’ Zane turned down an offer by Tommy Hilfiger to star in a nonunion ad campaign. Spears and ‘N Sync also donated part of the proceeds from concerts to the SAG Foundation after having taped a nonunion McDonald’s ad in Vancouver.

Although SAG and American Federation of Television & Radio Artists have signed more than 1,800 interim agreements, nearly all of them have been with smaller agencies and advertisers.

About 50 strikers picketed a nonunion casting call Monday at HKM Film in Hollywood for a pair of Visa spots. Additionally, dozens of union supporters passed out leaflets at Democratic Party evening events at the Peterson Automotive Museum and Paramount Studios.

Production drop continues

Figures released Monday showed that SAG and AFTRA have continued to pressure commercial production in Los Angeles during the strike. The latest figures for the first two weeks of August showed a 67% decline in permitted off-lot ad shoots to 83 production days compared with 249 in the same period last year, according to the Entertainment Industry Development Corp.

With the convention keeping shooting at a minimum this week and activists likely to picket any nonunion spots, the final August figure will probably wind up well below July’s total of 190 days — the lowest number since EIDC began tracking six years ago. For the first 15 weeks of the strike, ad shoots on public property have totaled 970 days, off 48% from the same period of 1999.