US President Bush has signed a law that offers American support for human rights groups in North Korea and for refugees leaving the secretive state.
Poverty and starvation are rife in North Korea
It earmarks $24m a year for such causes, and makes North Koreans eligible for asylum in the US.
Until now, they have been treated as citizens of South Korea, which still technically claims sovereignty over the whole peninsula.
North Korean has called the bill an attempt to bring down its government.
Symbol of support
The White House said in a statement that the North Korean Human Rights Act of 2004 was "intended to help promote human rights and freedom in the Democratic
People's Republic of Korea".
The law provides for financial support to non-profit groups promoting human rights, democracy, the rule of law, and capitalist development.
It also establishes a special envoy whose job it will be to monitor human rights in North Korea.
The BBC's Charles Scanlon, in the South Korean capital Seoul, says refugee groups have backed the law as an important symbol of support, although its practical impact could be limited.
The groups say it is unclear how and when the new funds will be distributed, and North Koreans will not be offered special treatment when they apply for political asylum.
At least 200,000 North Koreans are already estimated to have crossed the border into China, but they face repatriation if caught by the Chinese authorities.
Our correspondent says both South Korea and China are uneasy about the new law, as neither wants to encourage a bigger flow of refugees.
Congress has made clear that in passing the law, it wants human rights linked to negotiations on North Korea's nuclear weapons programme.
US Secretary of State Colin Powell is due to visit the Far East at the weekend to try to kick start talks with North Korea and other nations on Pyongyang's drive for nuclear weapons.