The Swiss National Bank, battling a rise in the country's currency, could push interest rates further into negative territory if the franc moves in the "wrong direction", a Swiss newspaper reported on Sunday, citing sources close to the bank.
Citing sources close to the SNB, Schweiz am Sonntag said "a rate of minus 1.5 percent is being considered".
A spokeswoman for the SNB declined to comment on the story.
In a bid to discourage investors from piling into the safe-haven Swiss franc, the SNB said in January it would charge even higher negative interest rates of minus 0.75 percent on some of the banks who deposit funds with it.
Negative rates effectively mean banks are paying the central bank to hold their money.
This move on January 15 was announced alongside the SNB's abandonment of its cap of 1.20 francs to the euro, which sent the value of the franc soaring.
Switzerland's currency could also face renewed upward pressure when the European Central Bank begins its new government bond-buying programme on March 9.
SNB Chairman Thomas Jordan had said in February the central bank has room to lower already negative interest rates if necessary to weaken the franc.