NEW YORK (AFP)- Five leading banks are close to agreements with regulators to pay billions of dollars over charges they rigged the foreign exchange market, a person close to the talks said Thursday.

US and British regulators are finalizing separate accords with Barclays, Citigroup, JPMorgan Chase, Royal Bank of Scotland and UBS in the long-running probe over allegations that they conspired to fix the US$5.3 trillion forex market, the source said.

The size of the fine will range by institution with some banks paying hundreds of millions and the most egregious violators paying more than US$1 billion. A deal could be announced as soon as next week, according to the source.

Regulators involved include the British Financial Conduct Authority, the US Federal Reserve, the US Department of Justice and the New York Department of Financial Services, the state banking regulator.

UBS will pay a penalty under the settlement, but has received immunity from prosecution because it cooperated with US officials.

Regulators have been pushing for the four other banks to plead guilty to the charges, although this point is still under negotiation, the source said.

The penalities are expected to be higher for Barclays, which did not participate in a US$3.2 billion agreement announced last November between Britain's Financial Conduct Authority and the US Commodity Futures Trading Commission and five banks over foreign exchange market rigging.

The sprawling forex probe has ensnared most large banks and centered on accusations traders conspired through instant messages and online chats to manipulate the market in ways that cheated clients and bolstered their own profits.