He said he had held talks with the North's nuclear envoy, Ri Gun, and other senior officials.
Harrison said he was also told that "North Korea wants friendly relations with the United States" and that if the Obama administration makes a political decision for improved relations, then "the DPRK [Democratic People's Republic of Korea] and the United States can become intimate friends".
A North Korean foreign ministry statement carried by the state-run Korean Central News Agency said on Saturday the country's priority was to build up its "nuclear deterrent force" to protect itself and not to normalise diplomatic ties with the US.
A spokesman said even if diplomatic relations with the US were improved, North Korea's "status as a nuclear weapons state will remain unchanged as long as it is exposed even to the slightest US nuclear threat".
"We can live without the normalisation of ties with the US, but we cannot survive without the nuclear deterrence," the spokesman said.
The government vowed on Tuesday not to give up its nuclear weapons until the US drops its "hostile" policy, and called for "free field access" to ensure there are no US
atomic weapons in South Korea.
North Korea has pledged several times to get rid of its nuclear programme, but disarmament talks have failed for the past 15 years, despite offers of aid in exchange of disarmament.
|Harrison said North Korea's weapons are "off-limits" to arms inspectors [Reuters]
Relations between North and South Korea have been frosty since Lee Myung-Bak came to office as president in the South on a promise to "get tough" on the communist neighbour.
South Korea denies taking a confrontational stance and has repeatedly called for dialogue with the North.
The North has threatened to reduce its neighbour "to ashes", but there has not been a major military clash since naval skirmishes killed dozens of sailors on both sides in 2002.
Hillary Clinton, US president-elect Barack Obama's designated secretary of state, has said the new US administration will pursue a "very aggressive effort" against North Korea's alleged atomic weapons proliferation.
She backed six-party talks which began in 2003 with the two Koreas, the US, China, Russia and Japan, but has indicated there could also be bilateral contacts.
North Korea tested an atomic weapon in October 2006. State media regularly accuses the US of plotting an attack on the country.