The US Congress is working to pass a spending bill that means the government will continue to be funded.
In shutdowns, government employees are vulnerable to furlough, or temporary unpaid leave.
"I don't think it'll happen because most people realize that government shutdowns are not in anybody's interest", Portman said.
Any federal employees sent home wouldn't be paid during the shutdown, but Congress has traditionally agreed to reimburse them once lawmakers can pass a new budget. Should the two parties not iron out their disagreements on government funding and immigration, a shutdown showdown would be upon us once more.
A shutdown only affects funds annually appropriated by Congress, not funding that is sustained long-term.
While core functions would not be affected, some Social Security Administration employees would be placed on furlough and minor services would be frozen. Workers will receive back pay, however, for any time missed because of a shutdown.
"Non-essential" federal agencies and workers.
But the Securities and Exchange Commission and the Commodity Futures Trading Commission, which police financial markets, could be hit.
But she said services at parks that require staffing and maintenance, such as campgrounds, full service restrooms and concessions won't be operating if there's a shutdown. Federal contractors with money still in the pipeline would also continue to work as long as they don't require access to federal facilities.More news: Twitch Teaming With Disney Digital Network and Creators For Exclusive Content
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Some financial regulators would get through a shutdown unscathed, although others might not.
However, Office of Management and Budget (OMB) director Mick Mulvaney said on Wednesday that a shutdown under the Trump administration "would look very different than it would under the previous administration", adding that national monuments would remain open.
During the 2013 shutdown, the Internal Revenue Service furloughed 90 per cent of workers, according the liberal Center for American Progress. And there have been shutdowns where an estimated $24 billion in economic output was lost.
MAIL DELIVERY: Deliveries continued as usual because the U.S. Postal Service gets no tax dollars for day-to-day operations.
Will air travel be affected? The Administrative Office of the U.S. Courts has said federal courts could continue to operate normally for about three weeks without additional funding. House Republicans on Wednesday afternoon signaled they may support another short-term spending bill that would fund the government until February 16, but also rollback some Obamacare taxes and extend the children's health insurance program (CHIP), reported the Washington Post.
Payments to doctors and hospitals under the health care programs for senior citizens and lower-income residents would continue. A program at the U.S. Centers for Disease Control and Prevention to track flu outbreaks was temporarily halted. Don't plan on enrolling in an NIH clinical trial until the shutdown is over.
CHILDREN: Six Head Start programs in Alabama, Connecticut, Florida, Georgia, Mississippi and SC serving about 6,300 children shut for nine days. There were delays in the review process for new applicants.
Site inspections by the Environmental Protection Agency and Food and Drug Administration. Agricultural statistical reports ceased publication.