SEATTLE – There is no more time to wait.

That's the message from Gov. Christine Gregoire and other political leaders who announced a $4 billion spending plan Thursday to replace the aging State Route 520 floating bridge over Lake Washington, which would include tolls as early as next year.

Gregoire says the bridge is at risk of sinking in an earthquake or major windstorm.

"It is time… no… I would say it's past time for us to step up and fix the problem for the sake of our families, for the sake of our growing, powerful economy… that is so dependent.  It literally is an economic bridge between two vibrant shores of Lake Washington," said Gregoire.

The governor is proposing to start constructing new floating pontoon sections as early as next year, with the whole bridge, including its connections to I-5 and 405, to be finished by 2018.

Gregoire says half of the expected $4 billion price tag would be covered by state and federal highway funds, the other half by tolls.

The new bridge would have two lanes in each direction, plus an extra lane in each direction for carpools and buses.

State Republicans have issues with the plan, saying other than the addition of an HOV and bus lane, the Governor's bridge plan doesn't add any capacity for cars.

"We don't want to under-build the bridge right now," said Rep. Doug Ericksen, deputy Republican leader. "The governor's plan unfortunately, scales back the size of pontoon. So even for this massive investment, she's talking about the only additional capacity you get is an HOV lane in each direction."

Voters in the region rejected a plan that would have provided more than $1 billion toward the $4 billion replacement bridge. The state and federal government already are on the hook for about half the cost.

The governor said motorists will need to pay the rest through tolls on the existing bridge, with cheaper tolls during off-peak hours. Gregoire's plan doesn't spell out how much the toll should be, although a recent study suggested between $5 and $10 roundtrip during rush hour.  It's also not clear if the Interstate 90 floating bridge would also be tolled to pay for the new 520 bridge.

(The Associated Press contributed to this report)