The $85 billion in across-the-board cuts, mandated by a 2011 deficit reduction law, apply in equal measure to defense and non-defense spending.
The do not apply to about 70 percent of the money spent by the U.S. government, which includes Medicare, Medicaid, Social Security and interest on government debt.
According to the White House budget office, the cuts translate into a 9 percent cutback for non-defense programs and a 13 percent reduction for defense programs, crammed into the next seven months.
President Barack Obama and administration officials have warned in a series of appearances of threats to U.S. defense readiness, long delays at airports, cargo held up at ports of entry, and parents scrambling to find child care if the spending cuts are allowed to go through.
The full impact will depend on whether Congress votes to end or mitigate the reductions or lets them run their full course.
On the assumption that they last at least seven months, here is a sample of the consequences drawn from rough estimates submitted by major agencies to the appropriations committees of the U.S. House of Representatives and the U.S. Senate.
Department of Defense
* Freeze civilian hiring, which currently amounts to about 1,500 to 2,000 people per week. Layoff temporary employees with as many as 46,000 jobs affected.
* Cut more than $10 billion in funding, mostly to contractors involved in maintenance and renovation of Department of Defense facilities around the country.
* Cancel a proportion of ship and aircraft maintenance work for the third and fourth quarters of the 2013 fiscal year that ends September 30. Reduce training and maintenance for Army units, which will put them at "at reduced readiness levels."
* Cut one third of naval operations in the Pacific. Reduce flying hours for Air Force pilots.
* Cut $3 billion in health care for military personnel and retirees which could lead to "denials of elective services" for active-duty dependents and retirees.
Cut roughly 9 percent in 2,500 weapons development programs.
Federal Aviation Administration
* Furlough all FAA employees for a total of eleven days, with as much as 10 percent of the workforce of 40,000 not working on "any given day," causing slowdowns in air traffic control operations and delays for travelers. Impose a hiring freeze across the agency.
* Reduce by $136 million FAA capital expenditures for maintenance and modernization of air traffic control systems, resulting in a slowdown in development of the NextGen satellite-based navigation system.
U.S. Customs and Border Protection
* Furlough of customs and border patrol workers for between 12 and 14 days, significantly increasing wait times for visitors at airports and other ports of entry.
* Downsize the workforce by 2,750 customs officers and 5,000 border patrol agents.
Transportation Security Administration
* Seven day furloughs for TSA screeners, increasing airport security line wait times by as much as an additional hour.
Department of Agriculture
* USDA has said it will need to furlough 8,400 meat inspectors, although details of how the furlough would be implemented are still emerging. USDA has said the cuts would deny food aid to 600,000 pregnant women, new mothers and infants. Production of the Census of Agriculture would be delayed.
Department of Justice
* Cut spending by $1.6 billion, with furloughs equivalent to the loss of about a thousand federal agents. Fourteen days of furlough for the FBI.
* Attrition of 145 attorney positions leading to fewer criminal and civil cases.
Social Security Administration
* Furlough most of the workforce for ten days or more, causing delays in processing of retirement and disability claims and early closing of some Social Security offices.
Internal Revenue Service
* Unspecified numbers of furloughs particularly at IRS call centers and a decrease in enforcement activities by IRS agents.
Centers for Disease Control and Prevention
* Cut of more than $350 million, resulting in 25,000 fewer breast and cervical cancer screenings for low-income, high-risk women and about 424,000 fewer HIV tests.
Food and Drug Administration
* Reduction of $133 million in non-user fee funding, causing "significant reductions" in testing of imported food and medical products and cuts in oversight of domestic food safety.
* Cut of $750 million in funding for educational assistance to low-income schools serving more than a million students, with job losses for more than 10,500 teachers and aides.
* Reduction of $600 million in special education grants to states, resulting in layoffs by school districts of about 7,400 special education teachers and aides.
Federal Emergency Management Agency
* Reduction of over a billion dollars in FEMA's Disaster Relief fund, resulting in the agency having to restrict hurricane season aid to immediate needs.
* Reduction of $120 million in grants to state and local agencies, causing layoffs of emergency personnel and first responders.
National Parks, forests and wildlife refuges
* Closures and limited access hours for some facilities and complete closure of 128 national wildlife refuges. Possible closure of campgrounds, trails and other recreational areas when there is insufficient staff to provide security.
Environmental Protection Agency
* Slow down in clean up programs for the Great Lakes, Chesapeake Bay and Puget Sound.
* About 1,000 fewer inspections for enforcement of clean air and water laws.
U.S. Embassy Security
* Cut to embassy security of $168 million. Delay in upgrades of 80 facilities.
(Compiled by Fred Barbash; Editing by Tim Dobbyn)