Han Song Ryol, Pyongyang's deputy permanent representative to the United Nations, said Washington was imposing sanctions in a "roundabout way" by recently beefing up enforcement against any exports of drugs and counterfeit currency by North Korea.

North Korea "will be left with no option but to take self-defense steps" to cope with the new US pressure, Han said in a hard hitting speech before lawmakers, State Department officials and diplomats at a symposium held at the Rayburn Office Building of Congress.

"Recently, the United States is putting into practice sanctions blocking the legitimate financial transactions of the DPRK (North Korea) based on the false charges of illegal deals such as drug deal and counterfeit notes," Han said.

This was to "put international pressure upon it" and "indicates that the US remain unchanged in its real intention to bring down the system in the DPRK," he told the forum organized by the Institute for Corean-American Studies (ICAS), a non-partisan think tank.

Han charged that "by applying sanctions against North Korea in a roundabout way," the US was pressuring Pyongyang to abandon its nuclear weapons at the fifth round of six-party nuclear talks to be held in Beijing next month.

He reminded the United States of a previous declaration by North Korea that it would regard any US sanctions against it as a "declaration of war."

Pyongyang would not abandon its nuclear weapons unless mutual confidence and trust are built between the two countries, he said.

The United States has of late been stepping up pressure on Kim Jong Il's regime to curb the North's exports of missile parts, drugs and counterfeit currency that US intelligence reports say are its main source of revenue and the way it finances its nuclear program.

For the first time recently, Washington formally cited Pyongyang in a US court for allegedly mass-producing counterfeit 100 dollar bills, known as Supernotes.

The United States has also urged nations from China to the former Soviet states to deny overflight rights to aircraft from North Korea that reportedly carried weapons technology.

Han's statement Thursday further clouded prospects of any breakthrough in the upcoming six-party talks among the United States, Russia, China, Japan and the two Koreas.

At the last round of talks in Beijing in September, North Korea agreed to a statement of principles under which it would give up its nuclear weapons in return for energy and security guarantees.

But soon afterward, Pyongyang said it would not dismantle its nuclear arsenal before the United States supplies it with a light-water atomic reactor to generate electricity.

The United States maintains that any discussions on a peaceful nuclear program for North Korea could take place only after Pyongyang disbanded its nuclear weapons arsenal.

Han rejected US suggestions that North Korea voluntarily submit an inventory of all its nuclear weapons and manufacturing facilities under any plan to abandon its nuclear arms program.

"The DPRK and the US now are at war technically and there exists tremendous filed mistrusts between them," he said.

"Under these circumstances, the DPRK cannot accept the demand to reporting its nuclear weapons voluntarily," Han added.

Curt Weldon, the vice chairman of the House Armed Services Committee and the first lawmaker to lead a congressional delegation to North Korea, hosted Han to a luncheon accompanied by several other legislators from both sides of the political aisle.

Weldon said the discussions were aimed at having a closer understanding of the American and North Korean positions in relation to the nuclear dispute.

Han declined to meet the press and as he was leaving the room, a North Korean defector heckled him and waved a placard "The only way for peace in the Korean peninsula is toppling Kim Jong Il."