US President Donald Trump has called on the UN Security Council to impose tougher sanctions on North Korea to resolve the crisis.
North Korea conducted a big live-fire exercise on Tuesday to mark the foundation of its military as a US submarine docked in South Korea in a show of force amid growing concern over the North's nuclear and missile programmes.
Speculation had mounted that the DPRK could carry out a sixth nuclear test or another missile launch, as in the past, to mark 85 years since the founding of its army.
TRT World's Sarah Jones has more.
Washington has sent the aircraft carrier USS Carl Vinson to the Korean peninsula, where it is expected to arrive – after a derision-provoking delay – later this week.
Confusion had clouded the carrier's whereabouts earlier this month after US officials indicated it was sailing towards North Korea when in fact it was heading south.
The vessel will take part in joint naval drills with the South's forces to "demonstrate Seoul and Washington's strong determination to punish North Korean provocations," the South Korean Navy said in a statement.
Trump has said the US was sending an "armada" to the Korean peninsula, including submarines.
Increasing pressure on China
The US has long pushed for China, the North's only major ally and biggest trade partner, to make more efforts to curb its behaviour.
But Beijing has resisted, concerned that a regime collapse could trigger a flood of refugees across the border and leave the US military on its doorstep.
However, in February China announced it was halting all imports of coal from North Korea – a crucial earner for Pyongyang – for the rest of the year.
"The steps we're seeing China take, in many ways unprecedented steps, bringing economic pressure to bear on North Korea are very welcome," US Vice President Mike Pence said Saturday.