Los Angeles City Councilman Tom LaBonge said Wednesday that he will call for a countywide parcel tax, designed to raise $1.7 billion, to help make long-term improvements to the region's transportation system.

The proposal came as the council's Transportation Committee recommended approval of an 18-month process to develop a 20-year transportation plan.

But officials said the tax proposal would need support from all cities within Los Angeles County, as well as from county supervisors.

Holding up a $1 bill, LaBonge said he will propose the countywide parcel tax of $52 to fund solutions to traffic congestion. Coupled with that, he said, officials would seek to lift a ban on heavy-rail construction that has constrained transit planners.

``I want to see us not only build a subway to the sea, but subways from the Valley to downtown, down to San Pedro, everywhere in the city,'' LaBonge said.

LaBonge said he does not yet have a specific plan and has not prepared a proposal to submit the parcel tax to other jurisdictions in the county and to place it on a ballot for voter approval.