North Korea is likely to carry out more missile tests if they "don't feel satisfied" with US talks.
That's according to US Defence Secretary Mark Esper, who added that it was important to "get serious".
"I've been watching the Korean Peninsula for maybe a quarter of a century now. So I'm familiar with their tactics, with their bluster and I think we need to get serious and sit down and have discussions about a political agreement that denuclearizes the Peninsula," he said.
Denuclearisation talks between both countries have reached a deadlock, with Pyongyang continuing to conduct a series of weapons tests over unrelenting sanctions from the US.
There are threats that North Korea could restart intercontinental ballistic missile (ICBM) testing, as US special envoy for North Korea, Stephen Biegun, urged Pyongyang to restart talks.
"I would like to remain an optimist that we can keep moving forward with regard to negotiations because the alternate is not a positive (one)," Esper added.


Trump says 'a whole civilisation will die tonight' if Iran does not make a deal
One attacker dead, two injured in gunfight outside Israeli consulate in Istanbul
French high speed train crashes into military truck, killing driver
Israeli military tells people in Iran to avoid using trains
Three killed after Russian drone hits city bus in Ukraine's Dnipro region