Washington Gov. Christine Gregoire says she'll decide within the next four weeks which option she'll back when it comes to replacing Seattle's Alaskan Way Viaduct, which carries Highway 99 along the city's waterfront.

Seattle's mayor and City Council want to replace the aging viaduct with a tunnel. State officials have said that would cost more than $4.5 billion.

But others - including a group of 30 Democrats in the Washington House of Representatives - want a new, elevated highway, which would cost an estimated $2.8 billion.

A letter from the Democrats to the governor said a tunnel "is a luxury the taxpayers can't afford."