Banks in the UK are braced to receive between £1bn and £2bn of fines this week for allegedly rigging currency markets, while US regulators are also expected to reach settlements before Friday.Six banks in the UK - Barclays, Citi, HSBC, JPMorgan Chase, the Royal Bank of Scotland and UBS - have confirmed they have set aside money to pay potential penalties issued by the Financial Conduct Authority for forex rigging and associated legal costs.The FCA, working with the Serious Fraud Office, is expected to announce a coordinated settlement.Last week, HSBC revealed it had set aside $378m for an FCA fine for breaches of "systems and controls" in its currency arm but cautioned that this sum did not relate to penalties to be imposed by other jurisdictions, particularly the US.The Commodity Futures Trading Commission (CFTC), the main derivatives regulator in the US, may levy fines of about $300m against each firm, depending on the level of their involvement, according to Bloomberg, which added that it was unclear how many firms may settle with the US regulator.In its latest results, Barclays showed it had ring-fenced aside £500m, more than the £290m the bank was fined for manipulating Libor in 2012, while RBS said it has set aside £400m.Having already been fined for rigging Libor, banks on both sides of the Atlantic have been investigated by regulators for colluding in the artificial fixing of benchmarks used by pension funds and money managers to determine the amount paid for foreign currencies in the £3.5tn-a-day forex market.?Bank of England governor Mark Carney said earlier in the year that the forex allegations were as serious as Libor, "if not more so because this goes to the heart of the integrity of markets".