Lagarde addressed EU leaders, meeting by videoconference to wrangle over how to engineer a recovery from the deep recession caused by three months of coronavirus lockdowns in most European countries.
In what ECB President Christine Lagarde described as a baseline scenario, the ECB sees the bloc's economy shrinking by 8.7 percent this year after much of Europe was shut down for over two months this spring to halt the coronavirus outbreak.
The central bank for the 19 countries that use the euro also extended its monetary stimulus program to at least the end of June next year, from the end of 2020 currently.
Lending growth to non-financial corporations accelerated to 6.6 percent in April, its fastest rate in over 11 years, from 5.5 percent a month earlier, the data showed.
Arguing that a "V"-shaped recovery was unlikely as movement restrictions may be lengthy, policymakers highlighted flexibility in the bank's 750 billion euro Pandemic Emergency Purchase Scheme, its flagship bond buying scheme during the crisis.
The Fed also said it would buy exchange-traded funds that hold high-yield debt, while the European Central Bank may also eventually adopt outright purchases of high-yield bonds.
German constitutional court ruled it exceeded its powers with its asset purchase scheme.
The verdict deals a blow to the 2-trillion-euro Public Sector Purchase Programme (PSPP) credited with keeping the euro zone economy afloat over the past five years.
But Weidmann, who also sits on the European Central Bank's rate-setting Governing Council, said that he did expect a sustained recovery once the pandemic was fully overcome.
In the extreme case that a recurring virus requires further damaging lockdowns, the US Federal Reserve and its peers float the whole boat -- government debt, corporate debt, perhaps even financing for mortgages and paychecks.
The slowdown, also marked by rapidly deteriorating labour markets, is likely to steepen before the recovery phase kicks in, she told the bank's post-policy meeting news conference.
More caution was evident in other asset classes, with the dollar steady against most of the other major currencies and German Bund yields - which move inversely to prices - dipping to a one-month low ahead of the expected ECB moves.
The latest Reuters poll, taken April 14-22, showed the bloc's economy contracting by 3.1 percent in the first quarter and 9.6 percent in the current quarter.
With much of Europe in lockdown amid the coronavirus outbreak, economic activity has come to a near standstill and markets have been in a tailspin, foreshadowing a deep recession on par with the 2008 global financial crisis and raising questions about the euro zone's cohesion at times of stress.
The ECB said it had allotted $75.82 billion in its new 84-day auction, introduced by major central banks last weekend in response to global demand for greenbacks, and $36.27 billion at its regular 7-day tender.
ECB President Christine Lagarde told a news conference the virus would have a "significant impact on economic activity" even if it is ultimately temporary in nature and called for "an ambitious and coordinated fiscal policy response".
On Monday, Italian banking stocks slid more than 12 percent and investors rushed to insure their exposure to the sector, driving up credit default swaps (CDS) for banks such as UniCredit and Intesa Sanpaolo by more than 40 basis points.
The sources acknowledged the ECB was under increasing pressure to lower its policy rate further after a surprise Federal Reserve cut on March 3.
Euro zone inflation has undershot European Central Bank's target of almost 2 percent for seven years. Some academics argue that the nature of inflation has perhaps changed, making super-low consumer price growth the new norm
"To think it's autopilot, that's ridiculous," Lagarde said on Bloomberg TV. "There's a forward guidance which is strong, which is setting a very clear timetable but it's fact dependent. Let's look at the facts, let's look at how the economy evolves."
Lagarde said that aim will now be reviewed, along with the ECB's toolkit, how it measures price growth and how it communicates with the public.
"The UK is due to leave the European Union on 31 January 2020. This means one less uncertainty, which is good news for investors. That said, the biggest challenge is yet to come namely the issue of reaching a trade deal between London and the EU during the 11 month transition period," she said.
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The 72-year-old Italian banker is widely credited with saving the euro zone from collapse, but some critics say he also overpowered opponents and tended to front-run the bank's monetary policy in public.