[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2008/images/08/14/art.obama.firefighters.jpg caption=" Obama spoke to the International Association of Firefighters in March."]
(CNN) – A major firefighters union will throw its support behind Barack Obama during its annual convention in Las Vegas on Thursday.
Obama, who is on vacation with his family in Hawaii, taped a message that will be played in front of the 3,500 members of the International Association of Fire Fighters at around 2pm E.T.
The union chose to back Obama over John McCain because of the presumptive Democratic nominee’s support of collective bargaining, which gives workers the right to jointly work with their employers to negotiate hours, salaries, benefits and overall working conditions, IAFF spokesman Scott Treibitz said.
“It is unacceptable when fire fighters do not have collective bargaining rights. But it's not just collective bargaining,” Obama said in the video. “For too long on too many issues, fire fighters have not been treated with the dignity, respect and honor you deserve."
The IAFF endorsed Sen. Chris Dodd’s ultimately unsuccessful presidential bid last August and IAFF President Harold Schaitberger campaigned with him in the early primary states. The union was also credited with giving Sen. John Kerry’s campaign a major boost in 2004.
"On every issue important to fire fighters Senator Obama is and has been in our corner," Schaitberger said. "We can't overlook Senator McCain's service to our country, but we also can't overlook his poor record on issues critical to the financial security of our 290,000 members."
Sen. Joe Biden will attend and address the convention on behalf of Obama.