Interestingly enough, and as far as i can tell, you CANNOT buy Petro with USD. You can use crypto (BTC, ETH, XEM), EUR or RUB.
This actually makes sense, also to protect buyers: the risk of seeing the SWIFT dollar transactions blocked by the well known world "democratic" tyranny is very high, after they imposed sanctions.
This sure makes sense, given that more than 52% of the "certified" offers where in USD and that euro and ruble transfers use SWIFT too.