The Marshall Islands' pension fund could be bankrupt by 2020.

The US-based firm Investor Solutions has managed the Marshalls' Social Security Administration investments since 2003.

The head of Investor Solutions, Frank Armstrong, has told Radio Australia's the fund's liabilities have existed for some time.

But he says with the stock market down, the amount of money the government needs to withdraw to pay benefits to retirees has become unsustainable.

"Up until last year tax receipts exceeded the dispersals, so it was relatively easy to go along and not solve the problem," he said.

"They've reached a tipping point now where they're going to have to start dipping into their accumulated funds and that problem only gets worse and worse.

"So they're going to have to make significant changes to their funding liabilities."

Mr Armstrong says the economic management of the fund is sound, but the government has so far been reluctant to act.

"This is a political problem, not an economic one," he said.

"Politicians being what they are, they're all aware that not a single thank-you card is going to arrive as a result of fixing the problem.

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Marshall Islands social security headed for crisis