Foreign Affairs officials told politicians a letter sent to Australia by North Korea showed it was "more isolated and under pressure" than ever.
"We do not usually get letters like this... this reflects a degree of pressure being applied in North Korea," DFAT official Graham Fletcher told a Senate estimates hearing in Canberra on Thursday.
"They are, I presume, trying to persuade us to change our policy [of sanctions]."
Earlier this month, North Korea sent an open letter to Australia through its embassy in Indonesia.
As it talked up its "nuclear arsenal", it sent "its compliments" to the Australian parliament but labelled US President Donald Trump a "threat to global peace".
Foreign Minister Julie Bishop released the letter to Fairfax and DFAT officials said they had not been told of its existence before.
"The letter was public before we found out about it," Mr Fletcher said.
"Normally, it would have been passed on. I think there must have been an oversight for it not to have been."
They also revealed the Australian government is forced to use archaic methods in its attempts to contact Kim Jong-un's nation.
"It's not unusual for them to be unusual," DFAT chief Frances Adamson said in response to questions from Labor senator Penny Wong.
"There are communications of various kinds; often, it has to be said, by fax machine … and occasionally by post."
The government said its sanctions regime against North Korea didn't mean there were "long periods of radio silence".
"We seek to communicate with North Korea probably every month or two about one thing or another," Mr Fletcher said.
"Following their nuclear test on September 3, we sent a number of notes to them through New York, Beijing and Jakarta to protest what they'd done and we sought permission to visit from our embassy in Seoul, which was not granted."
