The Los Angeles 2020 Commission, chaired by former U.S. Commerce Secretary Mickey Kantor and former deputy mayor and investment banker Austin Beutner, recommended that the nation's second largest city cut the projected return rate on its pension investments from 7.75 percent to 6 percent, the rate used by Buffett for Berkshire Hathaway's pension system.

Such a move would require the city to pay an extra $560 million a year into its two main retirement funds, said Miguel Santana, the city's administrative officer, who was not party to the report's recommendations.

Los Angeles projects its deficit next year at $240 million, and such a drop in the projected rate of return would pose a "significant challenge to the city," Santana told Reuters.

The lower the projected return rate, the more cities and employers must pay into retirement funds. Los Angeles's current 7.75 percent projected return rate is similar to that used by many other cities.

The portion of the city's budget spent on retirement costs has grown from 3 percent in 2003 to 18 percent this year. Unfunded liabilities - the amount of money the city has to pay to meet its long-term obligations - have increased to $9.4 billion in the past 10 years from $87 million, according to a recent report by California Common Sense, a budget watchdog.

Pension reformers argue that without more fully funding public pension systems now, some municipalities will face a crisis, and even bankruptcy, in the future because they will not have set aside the funds needed to pay retirement promises made to current workers.

In March, Buffett warned that the crisis in public pensions will intensify. The main reason, he wrote in a letter to shareholders, is that public entities have promised pensions they cannot afford.

The Los Angeles panel wrote: "Can anyone in City Hall claim to know more about understanding future liabilities and how to budget today for them than Warren Buffett?"

It is unlikely the pension recommendation will be adopted by the current mayor, Democrat Eric Garcetti, who is scheduled to give his first State of the City address on Thursday. Calls to his office were not immediately returned.

In its initial report in January, the commission said Los Angeles was faced with high poverty, crumbling infrastructure, terrible traffic, weak government, and unfunded pensions. It noted that LA is the only major U.S. city to show a net decline in jobs in the last decade.

The panel made a series of recommendations, including raising the minimum wage, merging the harbors of Los Angeles and Long Beach into a single port facility, and adopting a more transparent and responsible budgeting process.

(Reporting by Tim Reid; Edited by Ronald Grover; and Peter Galloway)

By Tim Reid