The US economy was expected to lose $3 billion from the partial federal government shutdown over President Donald Trump's demand for border wall funding, congressional researchers said.
800,000 federal employees returned to work yesterday after 35 days without pay.
The Congressional Budget Office said the cost of the shutdown would make the U.S. economy 0.02% smaller than expected in 2019.
More significant effects will be felt by individual businesses and workers, particularly those who scrambled to make ends after not being paid.
Overall, the US economy lost about $11 billion during the five-week period, the CBO said.
It expects $8 billion to be recovered, however, as the government reopens and employees receive back pay.
The longest shutdown in US history ended on Friday when Trump and Congress agreed to temporary government funding - without money for his US-Mexico border wall - as the effects of the shutdown intensified across the country.
The president had demanded that legislation to fund the government contain $5.7 billion for his long-promised wall.
He says it is necessary to stop illegal immigration, human trafficking and drug smuggling, while Democrats call it costly and inefficient.
A committee of Republican and Democratic lawmakers have scheduled an initial meeting on Wednesday, which will be open to the public, as they try to negotiate a compromise on border security before the February 15 deadline.
That session is likely to see little more than opening statements by lawmakers. Subsequent meetings could be conducted in private, where the hard bargaining would take place, several congressional aides said.
Trump said he would be willing to shut down the government again if politicians do not reach a deal he finds acceptable on border security.
On Sunday, he expressed skepticism such an deal could be made.
Trump has also said he might declare a national emergency to get money for the border wall. Democrats would likely challenge that in court.
Most employees should be paid by Thursday for back wages, which one study estimated at $6 billion for all those who worked without pay or were laid off on a temporary basis.
Contractors and businesses that relied on federal workers' business face huge losses, although some politicians are pushing legislation to pay contractors back as well.
