Less than two years after exiting bankruptcy, the city of Vallejo, California, is again facing a budget crisis as soaring pension costs, which were left untouched in the bankruptcy reorganization, eat up an ever-growing share of tax revenues.

Vallejo's plight, so soon after bankruptcy, is an object lesson for three U.S. cities going through that process today - Detroit, Stockton and San Bernardino, California - because it shows the importance of dealing with pension obligations as part of a financial restructuring, experts say.

The Vallejo experience may be particularly relevant to Stockton, which is further along in its bankruptcy case than Detroit and San Bernardino and has signaled its intention to leave pension payments intact.