The Bellevue City Council on Monday approved an agreement with a consulting firm to provide an independent estimate of the construction cost for a proposed downtown light-rail tunnel.

The contract with Hill International, for up to $250,000, will result in an estimate that can be compared with the estimate of Sound Transit, which will build and operate the East Link light rail line from Seattle, through Bellevue, to Redmond.

Last year, Bellevue and Sound Transit agreed to a term sheet calling for the two entities to split the projected $320 million in extra costs it would to build a downtown tunnel, compared with the cost of building a downtown street-level option. The independent estimate will be used as Bellevue negotiates a final agreement with Sound Transit later this year to jointly fund the tunnel.