Stock traders also seemed solidly against a shutdown. The Dow Jones Industrial Average fell by more than 120 points, or nearly 1 percent, and the other two major indexes also closed lower.
Among major economic issues that could result from a shutdown: delays in processing FHA housing loan applications -- a potential drag on the housing recovery -- and the potential loss of government spending that's helping prop up the economy, said Christine Romans, host of CNN's "Your Money."
"You've got an economy right now that's very tied to government spending and government contracts, so that could have a ripple effect all across Main Street," she said on CNN's "New Day."
If the government does shut down, it would be the first time it has happened in more than 17 years. That previous shutdown, sparked by a budget battle between Democratic President Bill Clinton and a Republican Congress, lasted for 21 days.
While the military will remain on duty, as will many essential public safety, health and welfare operations, many government offices will close. About a quarter of the federal government's 3.3 million employees -- those frequently referred to as "nonessential" -- will be told to stay home from work until the shutdown is over.
Attorney General Eric Holder and Defense Secretary Chuck Hagel said essential crime prevention and military services would continue, but some workers would be furloughed. Holder said he would cut his pay by the same amount as the most severely affected Justice Department employees because "we are all in this together."