The NSW government is open to a sale of the entire $16.8 billion WestConnex motorway project next year, in a move analysts say could boost the eventual price because of the high level of interest from large investors.

The possibility of offloading ownership of the whole 33-kilometre motorway before it is complete comes just two weeks after the government confirmed it was selling "at least a 51 per cent" stake in WestConnex by mid next year. The money raised will be used to fund the final stage of the motorway, which will link the M4 and M5 and cost more than $7 billion to construct.

Grilled on WestConnex at a NSW inquiry into toll roads, senior NSW Treasury official Leilani Frew said "all options" were on the table when asked whether the government could look at selling 100 per cent of Australia's largest motorway project.

She said the sale process was a balancing act between price and the amount of risk that remained with the government.