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.
US President Donald Trump held talks with Israeli Prime Minister Benjamin Netanyahu at the White House on Monday, while Israeli officials continued indirect negotiations with Hamas aimed at securing a Gaza ceasefire and hostage-release deal.
Search teams plodded through muddy riverbanks and flew aircraft over flood-ravaged central Texas as hopes dimmed of finding survivors from a disaster that has claimed at least 96 lives, many of them children.
Four workers were killed and at least 22 others were injured in a fire that broke out on Monday at a key data centre in Cairo, Hossam Abdel Ghaffar, the spokesperson at Egypt's Health Ministry, told Reuters on Tuesday.
President Donald Trump said on Monday the US would send more weapons to Ukraine, primarily defensive ones, to help the war-torn country defend itself against intensifying Russian advances.