WASHINGTON (AP) — Gridlock in Washington will lead to gridlock across the country if lawmakers can’t quickly agree on how to pay for highway and transit programs, President Barack Obama and his top officials warned Tuesday.

States will begin to feel the pain of cutbacks in federal aid as soon as the first week in August — peak summer driving time — if Congress doesn’t act, Transportation Secretary Anthony Foxx said in a letter to states. That’s because the balance in the federal Highway Trust Fund is dropping and will soon go below $4 billion, the cushion federal officials say is needed for incoming fuel tax revenue to cover outgoing payments to states.