Any city of the primary class may establish a fire and police pension fund. Such city may anticipate its liability for future pension payments on an actuarial basis and, in order to equalize the tax burden over a period of years, may levy and collect taxes in each fiscal year sufficient to meet current needs and equalize the future payments. The tax so levied and collected, together with contributions made by firefighters and police officers, shall be credited to the fund. Any unexpended balance remaining in the fund at the close of the fiscal year shall be reappropriated for the ensuing year. Pension payments required by law shall be a general obligation of the city and may be made out of, but not limited to, the fund.