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.
Ukraine issued air raid alerts for Kyiv and the country's eastern half as blasts shook the city of Mykolaiv early on Monday, authorities said, hours after the one-day Easter ceasefire declared by Russian President Vladimir Putin came to an end.
US Vice President JD Vance began a four-day visit to India on Monday and will hold talks with Prime Minister Narendra Modi, as New Delhi rushes to avoid steep US tariffs with an early trade deal and boost ties with the Trump administration.
The Israeli military on Sunday said a review into last month's killing of emergency responders in Gaza found there had been "several professional failures" and that a commander would be dismissed over the incident.
US President Donald Trump is threatening to cut another $1 billion in funding for Harvard University, this time targeting health research, the Wall Street Journal reported on Sunday, as the administration's row with elite schools escalated.