This earnings season, banks set aside more money for the rising cost of fines, lawsuits and compensation.
Authorities in the United States, Britain and elsewhere have so far fined UBS, RBS, Barclays, Rabobank and ICAP $3.7 billion for manipulating rates. Seven individuals face criminal charges.
The London inter-bank offered rate (Libor) and its European cousin (Euribor) are used to price hundreds of trillions of dollars in assets, from Spanish mortgages to derivatives.
A settlement with the EU over cartel allegations would require the banks to admit liability, potentially paving the way for lawsuits from investors and others who believe they have lost money because of the rates manipulation.
(Read more: UK court to hear evidence ahead of landmark Libor ruling)
Under the Libor settlement, the world's top interdealer broker, ICAP, and Dutch cooperative bank Rabobank are among those that will be fined, the person said. The names of the other two financial institutions were not immediately clear.
Switzerland's UBS will not be fined because it was the first member of the group to come clean during the European Commission's investigation into wrongdoing, two sources familiar with the case confirmed to Reuters.
European lawmakers have responded to public anger over the cost of bank bailouts with tough measures that include the first bonus cap in the world for bankers.
Almunia wants to hand out the fines by the end of the year, reinforcing his reputation for cracking down hard on banks' wrongdoings since the financial crisis struck five years ago.
"The total fine could be at least 1.5 billion euros ($2.02 billion)," the financial industry source told Reuters of the Libor settlement. That would beat the current record of 1.47 billion euro fine for a cartel involved with cathode-ray tubes.
(Read more: UK charges two brokers in Libor investigation)
The financial source said the group of banks had admitted to wrongdoing in yen Libor, the rate associated with the Japanese currency, in exchange for a 10 percent cut in the fine.
The fines, which can reach up to 10 percent of a company's global turnover, are nonetheless set to be significant.
RBS had a turnover of 25 billion pounds last year, while Barclays was 29 billion pounds and Rabobank 13.5 billion euros. ICAP's turnover was 1.47 billion pounds. RBS, Barclays, Rabobank, ICAP and UBS declined to comment.
The European Commission spokesman for competition policy, Antoine Colombani, declined to comment.
For its Euribor settlement, Brussels is also set to fine six global banks, including Deutsche Bank, JP Morgan, HSBC, RBS, Credit Agricole and Societe Generale, a source has told Reuters.
Barclays, which alerted the European Commission to the suspected wrongdoing in relation to Euribor, will not be fined.
(Read more: Banks and trust: No honor system here)
All of the banks named in relation to either settlement declined to comment.
Almunia's investigators say interest rate derivatives' traders colluded to rig the Libor and Euribor benchmarks, using advanced knowledge of the cost of borrowing to bolster their profits. Such cartels are illegal.
Libor is based on a survey of what banks would charge each other for loans. Other regulators have already found that traders colluded on answers that could nudge the reported rates by amounts that were tiny but translated into big profits.
In the Libor settlement, all the banks have admitted to wrongdoing to reduce the size of their fine, but in the Euribor settlement several of the banks are contesting the size of the proposed penalties.
HSBC, Europe's largest bank, is one of those, two sources said. In these cases, the banks are likely to face formal charges next month, followed by fines next year, one of the people said.