Biden has outlined a $1.9 trillion stimulus package proposal to jump-start the world's largest economy, which has been at the epicenter of the COVID-19 pandemic having lost over 400,000 lives, fueling optimism and sending Wall Street stocks to record highs on Thursday.

Hopes for an upswing in U.S. economic growth, helped by the huge stimulus plan, was reflected in the Jan. 19-22 Reuters poll of more 100 economists.

In response to an additional question, over 90%, or 42 of 46 economists, said the planned fiscal stimulus would boost the economy significantly.

"There are crosswinds to begin 2021 as fiscal stimulus helps to offset the virus and targeted lockdowns. The vaccine rollout will neutralize the latter over the course of the year," said Michelle Meyer, U.S. economist at Bank of America Securities.

"And upside risks to our...growth forecast are building if the Democrat-controlled government can pass additional stimulus. The high level of virus cases is extremely disheartening but the more that the virus weighs on growth, the more likely that stimulus will be passed."

Reuters poll graphic on the U.S. economic outlook

The U.S. economy, which recovered at an annualized pace of 33.4% in the third quarter last year from a record slump of 31.4% in the second, grew 4.4% in the final three months of the year, the poll suggested.

Growth was expected to slow to 2.3% in the current quarter - marking the weakest prediction for the period since a poll in February 2020 - amid renewed restrictions.

But it was then expected to accelerate to 4.3%, 5.1%, 4.0% in the subsequent three quarters, a solid upgrade from 3.8%, 3.9% and 3.4% predicted for those periods last month.

On an annual basis, the economy - after likely contracting 3.5% last year - was expected to grow 4.0% this year and 3.3% in 2022, an upgrade from last month.

Reuters Poll - U.S. economy and Fed monetary policy - January 2021 https://fingfx.thomsonreuters.com/gfx/polling/azgpoljbkvd/U.S.%20economy.PNG

Nearly 90%, or 49 of 56 economists, who expressed a view said that the U.S. economy would reach its pre-COVID-19 levels within a year, including 16 who expected it to do so within six months.

"Even without the stimulus package, we had already thought the economy would get back to pre-COVID levels by the middle of this year," said Jacob Oubina, senior U.S. economist at RBC Capital Markets.

"With the new stimulus package there will be more direct money in people's pockets, easily boosting the economy, provided a vaccine rollout progresses in a constructive manner."

But unemployment was not predicted to fall below its pre-pandemic levels of around 3.5% until 2024 at least.

When asked what was more likely for inflation this year, only one said it would ease. The other 40 economists were almost evenly split between "a significant pickup" and price pressures remaining "about the same as last year."

Still, the core Personal Consumption Expenditures (PCE) price index - the Federal Reserve's preferred inflation gauge - was forecast to average below the target of 2% on an annual basis until 2024 at least, prompting the central bank to keep interest rates unchanged near zero over the forecast horizon.

"I don't think it will be an increase in underlying (inflation) trend, it is sort of a rebound in prices that have been depressed during the pandemic," said Scott Brown, chief economist at Raymond James.

(For other stories from the Reuters global long-term economic outlook polls package:)

(Reporting by Indradip Ghosh and Richa Rebello; Additional reporting by Manjul Paul; Polling by Mumal Rathore; Editing by Rahul Karunakar and Hugh Lawson)

By Indradip Ghosh and Richa Rebello