Washington has removed North Korea from its list of countries sponsoring terrorism, US officials have confirmed.
A US State Department official said the deal was reached after North Korea agreed to provide full access to its controversial nuclear programme.
"Every element of verification that we sought has been included in this agreement," the official said.
The US blacklisting has been a major factor leading to deadlock over North Korea's nuclear disarmament.
State Department spokesman Sean McCormack said North Korea would resume its disablement of nuclear facilities.
This disablement was agreed to in 2007, but the process has recently reversed with North Korea threatening to restart its Yongbyon reactor.
Under the latest accord, North Korea will allow nuclear experts to take samples and conduct forensic tests at all its declared nuclear facilities and undeclared sites, on mutual consent, the statement said.
The North will also allow inspectors to verify that it has told the truth about transfers of nuclear technology and an alleged uranium programme - which North Korea has always denied.
There has so far been no response to the deal from North Korea.
Analysts say several previous deals have broken down over different interpretations over what is required, and it is by no means clear that this latest agreement will succeed.
Patricia McNerney, assistant secretary for international security and non-proliferation, said that verifying North Korea's nuclear programme would be "a serious challenge".
"This is the most secret and opaque regime in the entire world," she said.
Correspondents say critics will also question the timing of the agreement, giving the Bush administration a much-needed foreign policy advance in its final months.
The announcement comes after a visit to Pyongyang last week by US envoy Christopher Hill, and days of talks between the US and its negotiating partners China, South Korea, Russia and Japan.
Together with North Korea, they have been involved in long-running six-party talks over the de-nuclearisation of the Korean peninsula.
Tokyo had raised objections because North Korea has not resolved issues related to its abduction of Japanese citizens in the 1970s and 1980s.
"The key principle of the six-party talks is that any agreement must be agreed upon and in essence guaranteed. The next is to go to the six and have this formalised," Mr McCormack said.
Christopher Hill's visit to Pyongyang paved the way for the agreement
But removing North Korea from the US blacklist has been treated with scepticism by some conservative Republicans.
Republican presidential candidate John McCain - speaking before Saturday's announcement - said he would not support the step unless it was clear that Pyongyang would accept intrusive inspections of its nuclear sites.
"I expect the administration to explain exactly how this new verification agreement advances American interests and those of our allies before I will be able to support any decision to remove North Korea from the list of state sponsors of terrorism," he said.
North Korea began disabling its Yongbyon nuclear reactor in August, but more recently it has made moves to reassemble the plant after Washington refused to remove it from the terror sponsors' list.
In other provocative steps, it expelled UN inspectors and test-fired short-range missiles, heightening tensions with the US.
Correspondents say that Pyongyang wants to come off the US list in order to receive international aid and loans, and as a step towards its diplomatic rehabilitation.
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