But South Korean analysts said Kim decided not to conduct the nuclear test, instead holding a parade meant to show off North Korea's military might.
Previously, the North Korean military threatened to unleash a "merciless" response against American targets, including the naval task force the United States recently deployed.
Aside from improving the technology, North Korean missile and nuclear tests are seen by outside analysts partly as efforts to bolster the domestic image of leader Kim Jong Un and apply political pressure on Seoul and Washington.
But there had been fears that the isolated country would mark the Day of the Sun by conducting a nuclear test - in defiance of USA warnings not to.
The move, coupled with the US retaliatory strikes against Syria over a chemical weapons attack on civilians, touched off fear in South Korea that the United States was preparing for military action on the North.
"We're prepared to respond to an all-out war with an all-out war", said Choe Ryong-hae, believed to be the country's second most powerful official.
Donald Trump recently tweeted that "the problem of North Korea" would be "taken care of".
The weekend is just getting underway in the US, but already I have to say it was a good day.
Pence is due in Seoul at the start of a 10-day trip to Asia in what his aides said was a sign of the U.S. commitment to its ally in the face of rising tension.
An unidentified rocket is displayed during a military parade marking the 105th anniversary of the birth of late North Korean leader Kim Il-Sung in Pyongyang on April 15, 2017.
The arsenal of weapons on display included the new ballistic missile - which is thought to have a range of around 600 miles - and what appeared to be a battery of KN-08 and KN-14 missiles, which analysts believe could reach the USA mainland.
But this year the holiday came as tensions run high between North Korea and another world power. Kim did not speak during the annual parade, which celebrates the 1912 birthday of his late grandfather Kim Il Sung, North Korea's founding ruler, but a top official warned that the North would stand up to any threat posed by the United States.
North Korea showed two new kinds of ICBM enclosed in canister launchers mounted on the back of trucks, suggesting that Pyongyang was working toward a "new concept" of ICBM, said Melissa Hanham, a senior research associate at the US-based Middlebury Institute of International Studies at Monterey, California.
On Twitter, Mr Trump said he had "great confidence" China would "properly deal with North Korea". "He is doing the wrong thing", he said of Kim Jong-un. The country conducted two nuclear tests previous year.
Japan, the United States and South Korea are maintaining vigilance amid signs North Korea may conduct another nuclear test.
The North launched a ballistic missile from the same region earlier this month ahead of a summit between the United States and China to discuss the North's arms programme.