The ECB has missed its goal of keeping price growth "below but close to 2%" for a decade despite massive money printing, negative rates on deposits and subsidised loans to banks.
Inflation is now seen averaging 1.9% this year, above the 1.5% projected in March, while in 2022 it is seen at 1.5%, against an earlier projection for 1.2%.
"This evidence suggests that we should avoid withdrawing policy support - either deliberately or by tolerating adverse spillovers - until the output gap is closed and we see inflation sustainably back at 2%," Panetta said in a speech.
The ECB decided to continue running its Pandemic Emergency Purchase Programme (PEPP) at its current clip this quarter to keep borrowing costs stable for governments, companies and households.
While that decision was expected, analysts were awaiting hints about the pace of PEPP after June, after governors including the Netherlands' Klaas Knot raised the prospect of dialling it down.
The ECB has seen euro area inflation fall short of its near 2% target for eight years and expects to miss the target for years as the bloc emerges from the coronavirus crisis.
Nonetheless, he said there was room to improve guidance the ECB gives the market about how it aims to pursue its inflation target.
The sources said policymakers set on a monthly target for the its Pandemic Emergency Purchase Programme with a small tolerance band around it but agreed not to reveal it.
One of the sources said the ECB aimed to push down yields to where they were in December while another said improved economic prospects meant part of the recent increase in yields was justified.
The ECB already examines the suitability of board candidates in a so-called fit and proper assessment, but rules across the 19 euro zone members vary, so the quality of these checks can be inconsistent.
Supervisors will consider furthermore all of the diversity-related aspects that are most relevant to enhancing the individual and collective leadership of boards.