As the United States and North Korea offer contradicting claims over what caused talks between Donald Trump and Kim Jong-un to collapse in Vietnam, some diplomats are shifting the blame to one of the US President’s top advisors.

Former Australian Ambassador to South Korea Richard Broinowski says he has intelligence that national security advisor John Bolton stifled the summit – that was meant to focus on North Korea eventually dismantling its nuclear weapons – by adding an extra demand to negotiations.

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“The story goes from this very reliable and quite senior diplomat that he (Bolton) added a new demand to Donald Trump’s agenda,” Mr Brionowski told SBS News.

“He said to Trump that ‘you should not just insist on them abolishing their whole nuclear arsenal, but getting rid of their biological and chemical warfare arsenal as well.

Read More North Korea's offer to dismantle nuclear plant declined by Trump

According to Australian diplomatic sources, Donald Trump was said to be “unprepared” for such a demand, but put it to Kim Jong-un nonetheless.

“But Kim was even less prepared, and Kim just said 'we can't talk about that, that's not on the agenda’. And Trump peremptorily stopped the discussion at that point. They didn’t even get to substantive talks,” Mr Broinowski added.

“It seems to me that it would be a reasonable speculation that John Bolton, national security advisor, someone who is very conservative and doesn’t really want relations to get very far with North Korea may well have this put up to Trump as a spoke in the wheels and it could have well happened that way. We don’t know for certain.”

Contradicting claims over 'no deal'

North Korea has contradicted claims by US President Donald Trump over what caused the dramatic collapse of talks with Kim Jong-un.

The two-day summit in Vietnam ultimately ended in no deal - and no plan for Pyongyang to denuclearise its weapons program. A disagreement over economic sanctions on North Korea was ultimately to blame - but both sides are telling a different story.

Donald Trump says North Korea wanted all US and UN sanctions lifted in exchange for a partial dismantling of its nuclear weapons. Pyongyang, though, says proposed a partial removal of economic sanctions.

'Back to square one'

Dr Alison Broinowski, an Asian affairs expert at the Australian National University and wife of Richard Broinowski, believes the developments have put affairs “back to square one”.

“We can only hope that they can resume their efforts. But what we’ve been discovering recently, that’s a bit unlikely I think,” Dr Broinowski told SBS News.

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“In negotiations, everybody offers something and it’s less than what they want to offer and everybody gets something that is less than what they want to achieve. That’s just classic negotiations. They could have worked their way towards a meeting point. Something else has occurred."