The Minnesota Department of Transportation and Metropolitan Council are keeping a close watch on how the federal government will fund transportation in the wake of predictions that the Highway Trust Fund will go broke by August.

A report Wednesday by the pro-transportation investment group Transportation for America that said MnDOT stands to lose nearly $740 million in highway and transit funding if the fund goes dry.

The report said the state would have $113 million less to address traffic problems in the Twin Cities metro area when the federal fiscal year begins Oct. 1. Federal dollars make up 60 percent of the state’s transportation budget.

“We are able to manage a short-term problem,” MnDOT spokesman Kevin Gutknecht said. “It’s difficult for the long term. We need something stable.”

Gutknecht said many projects in the state’s 20-year highway improvement plan and transit initiatives are tied to federal dollars.

MnDOT is slated to get $18 billion over the next 20 years for road projects, but a report late last year by the Transportation Finance Advisory Committee said that the agency will need $30 billion to keep pace with population growth and aging infrastructure.

Minnesota has the fifth-largest highway system in the nation with 140,000 miles of roads. More than half of those miles and 35 percent of the state’s bridges are more than 50 years old.

The Highway Fund depends on revenue from the national gas tax of 18.4 cents per gallon, last increased in 1993. The Congressional Budget Office said that without new money dedicated to transportation, all money collected from the gas tax starting this fall will be needed to cover the federal share of projects already promised to states and transit agencies. There would be no money for new projects, the office said.

If funding remains at the current level, Transportation for America said that states and cities collectively face a $46.8 billion deficit. Already 10 states have raised taxes to create money for transportation, according to the Center for Transportation Excellence.

State Transportation Commissioner Charles Zelle and some DFL legislators have argued for a metrowide half-cent sales tax to be dedicated to transit investment.

This week the Obama administration sent Congress a four-year, $302 billion transportation bill that would keep the fund solvent.