North Korea gave the United States direct notification of its plan to fire a long-range rocket last week, a diplomatic source here said Sunday.

"North Korea informed the U.S. of the missile launch plan through the New York channel," the source said, requesting anonymity.

The New York channel refers to North Korea's U.N. representative office in New York, which has been used for working-level discussions, as the two sides have no official diplomatic ties.

The separate notification came around when Pyongyang announced its decision on Saturday (Seoul time) to launch what it claims to be a space rocket carrying a "working satellite" between Dec. 10 and 22.

"North Korea just gave a short briefing on its launch plan rather than providing specifics," added the source.

The U.S. government quickly denounced the North's move.

"A North Korean 'satellite' launch would be a highly provocative act that threatens peace and security in the region," State Department spokeswoman Victoria Nuland said in a statement.

North Korea is prohibited from carrying out any launch using ballistic missile technology under U.N. Security Council resolutions.

"Devoting scarce resources to the development of nuclear weapons and long-range missiles will only further isolate and impoverish North Korea," Nuland added. "The path to security for North Korea lies in investing in its people and abiding by its commitments and international obligations."

Despite protracted stand-offs with Pyongyang, U.S. officials said the New York channel remains open for bilateral communication.

In a related matter, Jeffrey Bader, who served as senior director for East Asian affairs on the National Security Council from January 2009 till April 2011, wrote in his memoir that Pyongyang delivered a "private message" to Washington on its plan to conduct a nuclear test in 2009. (Yonhap News)