Work on an important part of a new east-west highway corridor across south Renton that will help ease congestion could begin in spring 2012.

Key players in the project, including Renton, Tukwila, Boeing, Burlington Northern Santa Fe Railway and Sound Transit, held a high-level meeting Wednesday on the project, known as the Southwest 27th/Strander Boulevard Connection.

“The group decided to move forward with the project,” Rich Perteet, Renton’s deputy public works administrator for transportation, said of the verbal agreement.

The $20 million project spans less than a mile from where Strander Boulevard dead-ends just east of the West Valley Highway to near the Federal Reserve Bank in Renton, where it will connect to Southwest 27th Street.

But it’s the missing link in completing the full corridor to the East Valley Highway. Proponents were hurrying to come to a final decision to move forward or face the loss of millions of dollars in federal funding.

Sound Transit also is planning to develop its new Tukwila Station just to the north of the corridor, which also affected the project.

Next week, Renton and Tukwila, who are 50-50 partners in the project, will meet again to hammer out a revised interlocal agreement for the project.

Both cities also are working on an agreement with Burlington Northern for an underpass for the new roadway under the railroad tracks. The Union Pacific railroad tracks also are affected by the project farther to the east.

Perteet hopes to have the agreement with Burlington Northern done by the end of the year. Right of way would be acquired late this year and early next year, with a contractor beginning work in spring 2012. The project would be completed by the end of 2012.

Strander Boulevard is one of the major routes westward into Southcenter from the West Valley Highway just south of Interstate 405 in Tukwila. East of West Valley, it’s just long enough to give access to two restaurants.

The stubby Strander is blocked by jersey barriers; beyond those barriers is the Interurban Trail, the Burlington Northern tracks and finally Renton, where Strander becomes 27th Avenue Southwest.

The Federal Reserve Bank is visible in the distance.

The entire corridor project will cost between $60 million and $70 million. Renton’s share is expected to be no more than $4.5 million, Perteet said. Tukwila would contribute the same amount.

Burlington Northern also has plans to build a third rail line through the valley, Perteet said, but there’s no timeline for that yet. The line is necessary because of demands to carry more freight, he said.

That new line could affect Renton, too, because some of the Sound Transit station could end up in Renton, he said.

Renton and Tukwila also partnered in the 1980s to develop the South 180th Street corridor when the border between the two cities was straightened, he said. The Strander/27th Southwest corridor will help ease pressure on South 180th.

The Strander corridor could carry up to 55,000 vehicles in the future as the region grows, he said.

Also down the road are plans by the Washington state Department of Transportation to build a half-diamond interchange serving I-405 and Lind Avenue Southwest, Perteet said.