The new rules allow North Korea to export raw materials and goods to the United States and open air and shipping routes between the two countries.
While President Clinton announced plans to ease sanctions nine months ago, formal implementation did not take place until Monday -- less than a week after the historic summit meeting between the leaders of North and South Korea.
An announcement in the Federal Register said most items subject to government export regulations may be exported or re-exported to North Korea without a license.
The plan also allows U.S. companies to invest in agriculture, mining and a variety of other sectors in North Korea.
The announcement noted that the measure does not affect curbs relating the U.S. nonproliferation objectives or to North Korea's designation as a state sponsor of terrorism.
That designation bars U.S. non-humanitarian assistance to North Korea and also U.S. support for North Korea in international lending institutions.
Additional information about the impact of the new measures and other details were expected at a news briefing later in the day, officials said.
The timing of the announcement was widely seen as an attempt by the administration to build on the momentum generated at last week's summit meeting between North Korean leader Kim Jong-il and South Korean President Kim Dae-jong.
The summit produced an agreement to work toward the peaceful reunification of the peninsula and toward reuniting long divided families.
A Treasury Department fact sheet said the sanctions easing was designed to improve relations and to support a 1994 agreement under which North Korea vowed to freeze a nuclear weapons program and to substitute plutonium-producing reactors with safer light water reactors.
Another reason cited was to "encourage North Korea to refrain from testing long range missiles."
Following lengthy negotiations last summer, North Korea agreed to take that step in exchange for a U.S. commitment to ease sanctions.