Where was Kim Jong-un's nuclear button during Trump meeting?

Donald Trump and Kim Jong-un have finally had their meeting, but you have to wonder what was going on with their much boasted about nuclear buttons while they talked.

The US President and leader of North Korea began the year engaged in a war of words over their respective buttons.

Mr Kim said:" a nuclear button is always on the desk of my office," which was interpreted as a threat about his control over nuclear weaponry.

But Mr Trump responded in a tweet with a far more overt threat about his fire power.

"I too have a Nuclear Button, but it is a much bigger & more powerful one than his, and my Button works!"

It's well known that the American president takes his button wherever he goes in the form of a "nuclear football" carried by a staff member, 7 News reports.

But Mr Kim's camp is far more secretive and not much is known about how he's communicating with his home country while overseas.

According to 7 News it's likely a code system, but Griffith University nuclear expert Andrew O'Neil isn't sure about how he's communicating with home base.

"We don't know how developed North Korea's secure communications capabilities are, so whether Kim Jong Un will be within easy reach of his National Command Authority during his stay in Singapore is an open question," Dr O'Neil told 7 News.

Michael Madden, an expert with North Korea monitoring website 38 North, said he's very likely to able to launch from overseas, but in specific places.

"There are only certain designated facilities where these communications can be activated," he said.