The Federal Opposition says the Pacific Highway upgrade will be finished by 2020 if it wins government.
The Coalition is promising to inject $5.6-billion into the project, to cover 80 per cent of the remaining cost.
The Rudd Government says the arrangement should be a 50-50 split between the Commonwealth and state.
The Nationals' member for Cowper, Luke Hartsuyker, says the dispute has delayed the upgrade and made the original deadline impossible.
"The 2016 date has long gone and that's a really important difference for voters at the forthcoming election," he said.
"It would take, by the estimates of the New South Wales State Government, at least seven years longer if Labor is elected at the next election.
"So it's a huge difference for voters."
The commitment has been welcomed by the Pacific Highway Taskforce.
Chairman Richie Williamson says the group had taken out ads in local papers highlighting the need for more certainty about the project.
"In that was an open letter to Mr Abbott and the Prime Minister suggesting that a timeline needed to be committed to, and also a budget needs to be made available for that timeline," he said.
"The announcement today is something that the Pacific Highway Taskforce would certainly be welcoming."
But Labor's candidate for Cowper is accusing the Coalition of playing politics with Pacific Highway funding at a state and federal level.
Alfredo Navarro says the ALP has the by far the best record on Pacific Highway funding.
"$7.9-billion has been spent in six years, as opposed to $1.6 billion in 12," he said.
"That just shows exactly what's been going on.
"The documentation... it's in black and white, it says 50-50.
"They've agreed to it but they're not announcing that.
"If it has to be an 80-20 split?
"I'm more about getting the road done regardless of what the split is, but we have done it, we are doing the work."