Biegun also says North Korean leader Kim Jong-un committed during an October visit to Pyeongyang by U.S. Secretary of State Mike Pompeo, .to the dismantlement and destruction of North Korea's plutonium and uranium enrichment facilities.
If diplomacy doesn't work, the US has unspecified "contingencies", he added.
"It would be laughable if it weren't so scary", a former National Security Council official told INSIDER. Under the 2015 deal, Iran agreed to restrictions on its nuclear activities in exchange for the lifting of sanctions.
In his most detailed public remarks on his approach to North Korea after five months in his role, Biegun said the United States had told the North it was prepared to pursue commitments made in Singapore "simultaneously and in parallel" and had already eased rules on delivery of humanitarian aid to it.
Mr Coats also warned there was evidence that Kim Jong-un's regime was taking actions inconsistent with its declared support for denuclearisation of the Korean peninsula.
He pledged that once North Korea was denuclearised, the U.S. was prepared to explore with it and other countries the best way to mobilise investment in the country.
He broke with decades of USA policy when he agreed to meet with North Korean leader Kim Jong Un last June and has planned a second summit in February. Conversely, if the Iran agreement was worth doing, then why isn't one with North Korea?
"The capabilities and threat that existed a year ago are still there", said Lt. Gen. Robert Ashley, the director of the Defense Intelligence Agency. Trump's agenda during the summit is still not clear.
A draft Pentagon report expected to be released next week threw cold water on Trump's rosy assessment of the war against ISIS - upon which he based his decision for a rapid troop withdrawal from Syria. Recently, U.S. officials have signaled more flexibility.
"Some U.S. allies and partners are seeking greater independence from Washington in response to their perception of changing U.S. policies on security and trade", the report said, without providing examples or further explanation. Or the defeat of the Islamic state. Trump didn't fix that, but he tells us he did situation with Iran. The report predicted additional US -bound migration from El Salvador, Guatemala and Honduras, with migrants preferring to travel in caravans in hopes of a safer journey.
"It's important for the Republicans in Congress to recognise they have to weigh in with the president to say, 'You can't act without knowledge,"' Pelosi said.
The top intelligence officials assessed that Iran continues to abide by a nuclear pact it struck with world powers that curbed its nuclear program in exchange for billions of dollars in sanctions relief. Trump said that since ending the "terrible Iran Nuclear Deal, they are MUCH different, but a source of potential danger and conflict".
But one option not being discussed, he said, is the removal of US troops from the Korean peninsula. Negotiating are proceeding well in Afghanistan after 18 years of fighting.