Panetta said the ECB could and should keep credit cheap for a long time, even if borrowing costs around the world rise as a result of a booming US economy.
"For the ECB, this implies that we will have to maintain very favourable financing conditions well beyond the end of the pandemic period," he added.
The dollar index, a measure of the greenback's value against six other major currencies, hit as high as 92.919, its strongest level since November last year.
The euro slipped 0.2% in London trading at $1.1774, nearing last week's four-and-a-half-month trough of $1.1762. On a monthly basis, it is down 2.3%, its biggest drop since July 2019.
In a nutshell, the US economy is much stronger and miles ahead in the immunization game compared to Europe's and Japan's, and this ultimately translates into the Fed normalizing policy years before the ECB or the BoJ.