NSW Roads Minister Duncan Gay says the so-called Sydney gateway – a key component of the controversial $16.8 billion WestConnex motorway project – could be completed earlier than its scheduled opening to traffic in 2023.

Despite the proposal for a link to Sydney Airport and Port Botany forming one of the original justifications for WestConnex, the government has provided little detail on the exact shape of the "Sydney gateway".

Apart from providing a direct connection to WestConnex, the gateway has been cast as crucial to long-term plans to cope with worsening congestion on roads in and around the airport.

Mr Gay said the construction of the gateway would "come in on the end" of that for the M4-M5 link – the third and final stage of WestConnex – and "certainly we are open to be able to start it at different times".