UBS is expected to pay more than $450 million to settle claims some of its employees submitted false Libor rates, the New York Times reported earlier.
Britain's Barclays Plc was fined $453 million in June for manipulating Libor benchmark interest rates, and remains the only bank to settle in the investigation, which led to the resignation of the bank's chairman and chief executive.
U.S. and UK regulators, which released their settlements with Barclays at the same time, are working together on the UBS investigation and could release an agreement by the end of the year, although the timing could slip into next year, the person familiar with the matter told Reuters.
The reliability of the London Interbank Offered Rate, or Libor, has been cast into doubt by the rate manipulation accusations. Libor is intended to measure the rate at which banks lend to one another and is used as a benchmark for $300 trillion of contracts and loans across the world.
UBS was the first bank globally to report suspected rate rigging, and has said it has received conditional immunity from some authorities for cooperating in their probes.
A UBS spokeswoman told Reuters that the bank was in the midst of discussions with authorities in the United States and Britain in connection with Libor investigations and has been cooperating fully with the regulatory and enforcement authorities, but gave no further details.
Britain's Financial Services Authority declined to comment beyond confirming the already established fact that the FSA is investigating UBS.
The Commodity Futures Trading Commission and the U.S. Justice Department, investigating the Libor matter in the United States, declined to comment.
Other banks are also anxious to draw a line under the probe, which is well into its second year. British bank Royal Bank of Scotland said last month it hoped to reach a settlement on its part in the rate-rigging scandal - likely to result in fines for the bank - and expected to start talks soon.
Morgan Stanley has estimated that 11 global banks linked to the Libor scandal could face $14 billion in regulatory and legal settlement costs through 2014.
Switzerland is also investigating 12 U.S., European and Japanese banks suspected of conspiring to manipulate interbank lending rates. They include Credit Suisse, Deutsche Bank, HSBC Holdings and RBS.
"In Switzerland we are still investigating the case. We are in contact with other authorities," said Competition Commission official Olivier Schaller, but provided no further details.
Tobias Lux, spokesman for Swiss regulator FINMA, said the regulator was making efforts to clarify the issue, but declined to comment further.
Reuters parent company Thomson Reuters Corp collects information from banks and uses it to calculate Libor rates according to specifications drawn up by the British Bankers Association (BBA).
(Additional reporting by Sakthi Prasad in Bangalore; Editing by Mike Nesbit and Jane Merriman)
By Martin de Sa'Pinto and Steve Slater