If said assessments under section 3601 are not paid and said city does not proceed to collect said assessments by a sale of the lots or parcels of land upon which such assessments are made, or does not collect, or is in any manner delayed or defeated in collecting such assessments by a sale of the real estate so assessed, then the said city, in the name of said city, may maintain an action against the party so assessed for the amount of said assessment, as for money paid, laid out and expended, in any court competent to try the same, and in such action may recover the amount of such assessment with 12% interest on the same from the date of said assessment and costs.