I would like to use Interactive Brokers platform to buy forex futures. Suppose I buy forex futures AUD. The margin requirements for this futures contract is in AUD. My account does not have enough AUD cash to support this overnight margin requirement because most of my cash is in USD. Does this mean I have to pay interest to support the AUD margin requirement for the AUD futures contract even though there is enough cash in USD in the IB account? Should I convert some of my USD cash holdings into AUD to maintain enough AUD to support the margin requirement for the futures contract to avoid paying interest for the AUD margin requirement? I would like to keep as much USD as possible because of the high interest earned, thanks to Fed for raising interest rates in past years.