President Barack Obama has issued an executive order imposing new sanctions on North Korea, after its "illicit" nuclear test and satellite launch.
It freezes North Korean government property in America and bans US exports to, or investment in, North Korea.
The order also greatly expands powers to blacklist anyone, including non Americans, dealing with North Korea.
The 6 January nuclear test and 7 February satellite launch were violations of existing UN sanctions.
President Obama's order includes measures from the recently agreed UN Security Council sanctions - the toughest sanctions in decades against North Korea. But it also contains separate sanctions passed by Congress and enacted by the president in February.