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%.
As the economy rebounds and confidence improves, some policymakers are making the case for the ECB to start giving up its emergency measures and revert to more traditional forms of stimulus.
"We are committed to preserving favourable financing conditions. It's far too early and it's actually unnecessary to debate longer-term issues," Lagarde said on Friday.
US consumer prices increased in April as booming demand amid a reopening economy pushed against supply constraints, which could fuel financial market fears of a lengthy period of higher inflation.
The consumer price index jumped 0.8%; excluding the volatile food and energy components, the CPI soared 0.9%.
The aggregate growth of the 19 countries sharing the euro currency is likely to be 4.3% this year and 4.4% in 2022, the European Union's executive arm said, revising upwards its forecast from February of 3.8% growth in both years.
The forecast brings the Commission closer to the International Monetary Fund, which last month said it expected 4.4% growth in the euro zone this year.
The area has come under sharper scrutiny following the demise this year of supply-chain lender Greensill and Archegos, a family office run by former Tiger Asia manager Bill Hwang.
"What concerns me the most is that sometimes banks themselves don't have visibility on the portfolio of these entities," he said in an interview.
IHS Markit's flash Composite PMI Index, seen as a good guide to economic health, rose to 53.7 from March's 53.2, confounding expectations in a Reuters poll for a dip to 52.8.
Germany's 10-year government bond yield, the benchmark of the euro area, fell 1 basis point at -0.27%.
"Think of a patient which is out of a deep crisis but still on two crutches," Lagarde said.
"You don't want to remove either crutch, the fiscal or the monetary, until the patient can actually walk fine, and to do that means support well into the recovery."
There is a clear risk of self-fulfilling adverse dynamics taking hold, through which uncertain economic prospects induce households, firms and governments to hold back on expenditure plans, leading to a decline in overall demand that validates the loss in confidence about the future.
Hoping to prop up the economy until it is ready to reopen, the ECB has pushed borrowing costs to record lows through copious asset purchases and loans to banks at rates as low as minus 1%.
Still, IHS Markit's flash composite PMI, a closely-tracked economic indicator, bounced above the 50 mark separating growth from contraction to 52.5 in March compared to February's 48.8, its highest since late 2018.
Signs of a pick-up in the pace of the European Central Bank's bond purchases have also supported bond markets.