The tunnel, running from Little Hartley to south of Blackheath, has $2.5 billion committed to it by the NSW Government but will need Commonwealth Government money to make it a reality.

Mr Farraway had said previously that he would be writing to the new federal Infrastructure Minister about the tunnel project and he has since confirmed to Australian Community Media that he has done so.

"I have written to Catherine King, the new federal Infrastructure Minister, one, to congratulate her on her role and, secondly, to request a meeting to discuss a range of projects that we have in regional NSW that are in train and also projects that the NSW Government would like to pursue with the Commonwealth over the next few years," he said.

"The Great Western Highway has been specifically mentioned in my request for a meeting, and the letter, as an important project that we'd worked closely [on] with the former federal government and seeking their support for our preferred design and decision on a long tunnel."

Mr Farraway said he had not yet heard back from the new federal minister.

"But the request was made within days of Catherine King being sworn in," he said.

"We've requested the meeting and we've ensured that the Great Western Highway is at the top of the agenda."

The duplication of the Great Western Highway from Katoomba to Lithgow was announced by the NSW Government in the lead-up to the 2019 state election.

It said the duplication would improve safety, efficiency and freight access and cut travel times and the road toll.

The government announced in October 2020 that it would build a tunnel under Blackheath as part of that duplication and then said in May 2021 that it was investigating building a longer tunnel, bypassing Mount Victoria and Blackheath.

It confirmed in May this year that it would build the long tunnel, from Little Hartley to south of Blackheath, and that it would be toll-free.

The tunnel briefly seemed in doubt after a report from the independent Infrastructure NSW was released late last month in which it was recommended that a number of "mega" projects, including the tunnel, be put to one side.

But Deputy Premier Paul Toole and Mr Farraway have both stressed since nothing has changed in terms of the plans for the tunnel and the timeline for its design and construction.

While the tunnel still needs federal funding to go ahead, the duplication of the highway from Katoomba to Blackheath and from Little Hartley to Lithgow already has the required funding from the state and Commonwealth.

"We will announce the successful tenderer [for the duplication of the two sections] later this year and works will commence early 2023," Mr Farraway said.

He said the upgrade of the Great Western Highway from Katoomba to Lithgow was "important for the Central West, important for the Blue Mountains, but, most importantly, it's a critical road corridor for the state for freight, for connectivity over the Divide, and myself and the Deputy Premier have been very clear that we are very determined to see that project come to full fruition".

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