NASHVILLE (AP) - Republican Gov. Bill Haslam announced Tuesday that he will kick off a 15-stop tour of Tennessee to highlight the state's transportation funding challenges as he considers a proposal to increase the gas tax for the first time in 25 years.

Haslam cited a "multibillion dollar backlog" of highway projects across the state. He said the state can no longer depend on federal funding. He also said maintenance becomes more expensive as infrastructure ages and new projects are needed to improve safety, access and economic development.

"The good news is that all our vehicles get a lot better mileage than they used to," Haslam told The Associated Press at a National Governors Association meeting in West Virginia over the weekend. "The bad news is that there's a lot less money coming in."

"Like everybody else, we're going to have some serious infrastructure safety issues down the road," he said. "We just think it's time to start t hat conversation about what does that impact look like."

The governor is finding a familiar foe in the Tennessee chapter of Americans for Prosperity, the political advocacy group for Charles and David Koch, billionaire brothers who spend millions on conservative causes. The organization also took a lead in defeating the governor's Medicaid expansion proposal earlier this year.

Andrew Ogles, the group's state director, has launched a rival tour to speak out against any gas tax increase.

Ogles said the state could augment the road fund with revenues collected from areas other than the gas tax. He said the governor's recent decision to spend $120 million on a new state museum is an example of where money could have instead gone to transportation projects.

"I appreciate the governor's legacy project is the museum, however roads and bridges are more important," Ogles said in a phone interview. "We do not have a revenue problem. We have a spending and priority problem."

Haslam last month appeared undaunted that the group that helped defeat his Insure Tennessee is once again lining up against him on the gas tax.

"Have at it," the governor said. "That's how democracy works."

Tennessee's combined state and federal funding for highway spending was $337 per person in 2013, the sixth-lowest rate in the country. By contrast, 26 states spent more than $500 per person on highways that year.

Adjusted for inflation, the total state and federal highway spending in Tennessee increased by just 4 percent between 2003 and 2013.

Haslam will be joined by Transportation Commissioner John Schroer on the six-week tour beginning Aug. 5 in Memphis. Other stops are scheduled for Clarksville, Union City, Jackson, Nashville, Franklin, Kingsport, Greeneville, Shelbyville, Murfreesboro, Crossville, Chattanooga, Cleveland, Lenoir City and Knoxville.