By Paul Kiernan and Vivian Salama 

WASHINGTON -- The Trump administration's top economist said Wednesday that the U.S. economy may not grow at all in the first quarter if the partial government shutdown continues.

Kevin Hassett, chairman of the White House Council of Economic Advisers, noted in a CNN interview that first-quarter growth tends to be relatively weak because of measurement issues and said it could be "very close to zero" if the shutdown persists through March.

"It is true that if we get a typically weak first quarter and then have an extended shutdown, that we could end up with a number that's very, very low," Mr. Hassett said. He added that when the government reopens, the economy should recover any lost ground.

The White House estimates the economy loses "a little more than" one tenth of a percentage point of growth for each week that the partial shutdown persists.

Mr. Hassett's assessment of the shutdown's weekly impact lines up roughly with those of private economists. Michael Feroli, JP Morgan's chief U.S. economist, said earlier this month that the shutdown would shave between one and two tenths of a percentage point each week off quarterly gross domestic product growth.

A bigger question is how much of that lost growth might be recovered in subsequent quarters.

President Trump last week signed legislation promising back pay to the approximately 800,000 government employees who aren't receiving their paychecks during the shutdown. As a result, Mr. Hassett said any lost output during the first quarter should show up in second-quarter data, noting that the White House has left its forecast for 2019 GDP growth unchanged at 3%.

Mr. Hassett also said he sees the odds of a recession in 2020 at "very, very close to zero."

On Tuesday, Mr. Trump's economic adviser Lawrence Kudlow told reporters at the White House he's "not at all concerned" about the shutdown having a negative impact on the economy.

"No one likes the hardship that people are having to shoulder, including myself," he said. "But I will also say, we are predominantly not a government-run economy. We're a free-market economy. So when the government reopens...you will see an immediate snapback."

Other economists are less sanguine about the economy's capacity to bounce back fully, noting that the impacts of the shutdown are far-reaching and difficult to entirely account for.

The direct effects, such as delayed loans for small businesses or missed rent payments by government employees, are limited in scope.

But in an economy powered by spending and investment, which boil down to little more than consumers' and businesses' confidence in their future job and growth prospects, an extended shutdown could threaten broader collateral damage. A troubling sign that this risk may be materializing: The University of Michigan's consumer-sentiment index plunged 7.7% this month from December to the lowest level since Mr. Trump was elected.

"Federal employees will receive their back pay, but that doesn't mean that the businesses they patronize will be made whole by extra spending after the shutdown," said Ian Shepherdson, chief economist at Pantheon Macroeconomics, in a note to clients Tuesday.

Write to Paul Kiernan at paul.kiernan@wsj.com and Vivian Salama at vivian.salama@wsj.com

(END) Dow Jones Newswires

January 23, 2019 12:28 ET (17:28 GMT)