An unsolicited proposal from property and construction giant Lendlease to build a toll road linking Sydney Airport and Port Botany to the WestConnex motorway has been rejected, leaving the state's roads agency with the task of finding a solution.

The state government is understood to have decided against progressing the bid by Lendlease for the so-called Sydney Gateway through the unsolicited proposals process because the project would have required a large equity contribution or high tolls.

Aside from the prospect of a backlash from motorists, a higher than usual toll on the gateway threatened to push up the costs of transporting thousands of containers each week to and from the port by trucking companies and logistics operators.

The rejection of Lendlease's proposal leaves it up to Roads and Maritime Services to push ahead with building the gateway link, in a process similar to that under way for a major interchange for WestConnex at Rozelle in Sydney's inner west.