M5 extension to come 'months' early

Commuters in Sydney's southwest will get some traffic relief in the coming weeks with the first stage of the M5 extension being delivered months earlier than expected.

Premier Mike Baird announced on Wednesday that the first part of the $400 million widening will be delivered in a fortnight's time.

The first stage of the extension will add a third eastbound lane, stretching 4km, from Camden Valley Way to the Georges River Bridge in Liverpool.

Mr Baird says the announcement shows the government is serious about delivering much-needed infrastructure.

"If we say we are going to do it, we will do it," he told reporters in Sydney.

"If we see congestion, we will try and take it away."

Mr Baird says the first stage of the extension is being delivered months ahead of schedule.

Roads Minister Duncan Gay says the entire project is now 80 per cent complete.

"People of southwestern Sydney will be spending more home time and less traffic time," he said.

The entire 22km extension, which will add another lane to both sides of the M5, is expected to be completed by December.

Once finished, the government expects it to cut travel times by about 25 per cent.