Investors with as little as $3,000 have a new way to earn competitive interest rates on their money while keeping it fairly liquid and low-risk.

Central National Bank, based in Silver Spring, starting today will operate CNB Money Market Fund, offering interest rates pegged one percentage point below money market certificate rates, President Tom Moore said. Initially, that means investors could earn 14.9 percent on deposits of as little as $3,000 for terms as short as four weeks and as long as 12 weeks

The new instrument, Moore said yesterday, actually is a third category of deposit -- not a demand deposit (such as a checking account) or a saving deposit (which would earn much lower interest for the saver) -- authorized May 13 by the Comptroller of the Currency.

U.S. Treasury and other agency obligations purchased by the bank will be set aside to secure the CNB fund, he said.

In effect, the customer lends money to the bank, which puts up the securities as collateral for the loan. At the end of whatever term the investor selects, the bank agrees to repurchase those securities and pay the customer 14.9 percent interest for use of the funds. There is an interest penalty for early withdrawal.

No matter who you are, borrowing money is expensive these days, and this applies to banks, as well. What the new fund does for Central is give it a larger pool of available funds at lower cost.