The Federal Reserve Bank of New York was contacted by Barclays about the Libor rate setting as early as August 2007, according to Sky sources in the US who have been briefed on the matter.
It means that that particular branch of the powerful regulator may have known there was a problem with the benchmark rate months before it formally spoke to UK authorities about the issue in spring 2008.
The man in charge of the New York Fed at the time was Timothy Geithner, now chief of the US Treasury and one of the most influential men in global finance.
The New York Fed was not part of last month’s $453 million (£290m) Barclays settlement over manipulating Libor to make profit and avoid losses; that was orchestrated by other US regulators and the UK’s Financial Services Authority.
But questions will be asked about whether the Fed could have done more and sooner, especially given some of the requests for manipulating Libor rates came from Barclays traders in New York.
There will also be concern that any delay in marshalling intelligence between the multiple agencies involved may have resulted in a deepening of the 2008 financial crisis, or in more losses for consumers who had bought financial products pegged to the LIBOR rate.
Confirmation of the communication between Barclays and the NY Fed tallies with documents released by Barclays last Tuesday, which indicated members of its staff contacted NY officials with their concerns on August 28, 2007 and then ten more times up to October 2008.
Although no detail has been released about exactly what was said, this regular communication with both US and UK authorities has formed a central part of Barclays’ defence since the scandal broke.
The bank has said: "We believe that this chronology shows clearly that our people repeatedly raised with regulators concerns arising from the impact of the credit crisis on LIBOR setting over an extended period."
According to a person briefed on the matter, Mr Geithner was sufficiently concerned about the problem to hold a meeting on April 28, 2008 called "Fixing LIBOR" to "address issues we were seeing in markets to do with the LIBOR rate".
Officials at the Fed would not comment on the detail of that meeting, but in a statement released to Sky News, a spokesperson said: "In the context of our market monitoring following the onset of the financial crisis in late 2007, involving thousands of calls and emails with market participants over a period of many months, we received occasional anecdotal reports from Barclays of problems with Libor.
"In the Spring of 2008, following the failure of Bear Stearns and shortly before the first media report on the subject, we made further inquiry of Barclays as to how Libor submissions were being conducted. We subsequently shared our analysis and suggestions for reform of Libor with the relevant authorities in the UK."
On Monday a powerful congressional committee wrote to the New York Fed demanding transcripts of the communications between its staff and Barclays.
Sky News has seen a copy of the letter, written by chair of the Oversight Panel of the House Committee on Financial Services, Randy Neugebauer.
In it he highlights the testimony of former Barclays CEO Bob Diamond that his bank contacted US regulators repeatedly, and goes on to say: "Furthermore, some news reports indicate that although Barclays raised concerns multiple times with American and British authorities about discrepancies over how LIBOR was set, the bank was told not to stop the practice of suppressing rates."
The letter then asks for transcripts of all communication, in order "to get a preliminary understanding of the nature of discussions between Barclays and the NY Fed."
The move by this committee is the first real sign that the story is starting to gather steam on this side of the Atlantic.
The investigation is not over.
The US Department of Justice and the Commodity Futures Trading Commission, along with the FBI, are continuing to look at the role of other banks in LIBOR rate setting.
Those banks reportedly include Wall Street giants JP Morgan, Citigroup and Bank of America, as well as HSBC, Deutsche Bank and UBS.
Civil law suits have also been launched against banks reportedly being investigated which could cost them billions of dollars, according to the lawyers involved.