The US is giving its domestic agencies greater access to images from spy satellites, in a move strongly criticised by civil rights groups.
The images will be used to boost national security, disaster response and law enforcement, US officials said.
Use of the satellite imagery will be managed by a new office within the Department of Homeland Security (DHS).
Some US agencies already had limited access to the images, but many were restricted to scientific use.
The DHS says it wants to use the imagery to improve the quality of surveillance on borders, ports, bridges and other infrastructure.
Officials believe the satellites could identify and follow targets by their physical traits, and could be used to respond to disasters such as the 2001 attacks or Hurricane Katrina.
The Assistant Secretary of Homeland Security for intelligence analysis, Charles Allen, told the Washington Post the programme would be particularly useful in policing land and sea borders and in disaster planning.
Officials say use of the images for domestic law enforcement will be allowed only in limited cases, and a general ban on domestic spying by the CIA and the Pentagon will remain in force.
"This is not a system for tracking Americans," Mr Allen said.
Civil liberties activist Kate Martin, from the Center for National Security Studies, told the Wall Street Journal the program was akin to "Big Brother in the sky".
"They want to turn these enormous spy capabilities, built to be used against overseas enemies, on to Americans," Ms Martin said. "They are laying the bricks one at a time for a police state."
But Mr Allen dismissed privacy fears, saying: "Americans shouldn't have any concerns about it".