The United States Ambassador to South Korea says Washington must receive a complete nuclear declaration from Pyongyang before it can remove North Korea from American list of states sponsoring terrorism.   As VOA Seoul Correspondent Kurt Achin reports, an American ambassador says the North is failing to send a "clear signal" it intends to follow through on its promises.

U.S. Ambassador to South Korea Alexander Vershbow said Monday North Korea's delay in providing a promised nuclear declaration is causing frustration in Washington.

"There is a sense of impatience building up and we want to get on with it," Vershbow said.

In six-nation talks last year, North Korea agreed to provide a complete and correct list of all its nuclear activities and stockpiles before the start of 2008.  Negotiators from China, Russia, the United States, Japan and South Korea are still waiting for the document.

The declaration is part of a multi-stage agreement that seeks to trade energy assistance and diplomatic incentives with Pyongyang for gradual steps toward ending its nuclear weapons capabilities altogether.

The North has taken steps to disable its main plutonium-producing facility at Yongbyon and received hundreds of thousands of tons of fuel oil from the United States and its partners.  However, some experts say Pyongyang is hesitating on the declaration because Washington insists the North explain uranium-related activities it has never publicly admitted.

In this phase of the six-nation agreement, the United States pledged to lift a range of sanctions against North Korea and to remove it from a State Department list of nations accused of sponsoring terrorism.  Both steps would open doorways for the impoverished North to receive certain types of aid and investment which are currently banned.

Vershbow says Washington is ready to follow through, but needs North Korea to act decisively.

"We're ready to do that, but we aren't able to do that until we see a clear signal from the North Koreans that they are going to do their part with regard to the declaration," Vershbow said.

The United States, Japan and South Korea have all promised a new era in relations with North Korea, once Pyongyang fulfills the six-nation process of eliminating its nuclear arsenal.  The United States and Japan say they will normalize diplomatic ties, potentially opening the door to significant financial aid.  Newly elected South Korean President Lee Myung-bak has promised to help rapidly double per capita incomes in a non-nuclear North.