There were no further details, and the office said it was analysing the launch. Although China advocates for diplomatic outreach, the focus for now is on pressure.
North Korea revealed a suspected intercontinental ballistic missile Saturday, as the reclusive state marked its most important holiday with a first major military show since 2015, Anadolu reported.
China, the third party in what is becoming by the day an ever-more complicated diplomatic and military tangle, repeated its call for both sides to de-escalate tensions and agree to talks aimed at "de-nuclearising" the entire Korean Peninsula.
South Korea's Foreign Ministry said Han's remarks on the North's readiness to conduct a nuclear test and even go to war reveal the "true colors of North Korea's government that is bellicose and a breaker of regulations".
According to the adviser, the USA had good intelligence both before and after the launch.
Meanwhile, Vice President Pence is traveling to South Korea this weekend.
"As I said, Trump is always using aggressive words - it is the USA that is threatening us".
The official said that had it been a nuclear test, "other actions would have been taken by the U.S". Speculation has grown that it is to conduct a sixth nuclear test to coincide with the anniversary. The country launched a long-range rocket and conducted two nuclear tests past year, including its most powerful to date.
The Associated Press has quoted USA officials as saying the Trump administration will focus on working with China to raise pressure on North Korea rather than stepping in with military force. His visit comes just after a failed missile launch by the North.
Despite Beijing's key role in propping up North Korea, the Kim Jong-Un regime has repeatedly ignored warnings and sanctions from its powerful ally.
Pence is joined by his wife and two adult daughters and will lay a wreath at the Seoul National Cemetery and join USA and South Korean troops for Easter Sunday church services and a dinner.More news: Oil spill reported in Alaska, volume unknown
But the North Koreans aren't backing down either.
He criticized U.S. President Donald Trump's administration for "creating a war situation" on the Korean Peninsula by dispatching strategic military assets to the region.
Trump, who last week acted unilaterally in ordering a cruise missile strike on Syria, has been using America's military might to send a message to Kim.
Displaying more than one of the missiles indicates North Korea is progressing with its plan to base a missile on a submarine, which are hard to detect, said Joshua Pollack, editor of the Washington-based Nonproliferation Review.
As NPR's Merrit Kennedy reported earlier this week, the regime said it would "hold the USA wholly accountable for the catastrophic consequences to be entailed by its outrageous actions".
According to NBC News, citing several unnamed USA intelligence officials, the U.S.is prepared to launch a preemptive strike on North Korea using conventional weapons should Pyongyang conduct another nuclear test.
North Korea rolled out its military hardware Saturday at its annual Day of the Sun celebration commemorating the 105th birth anniversary of the country's founder, Kim Il Sung, the grandfather of current leader, Kim Jong Un.
State TV showed North Korea's Pukkuksong submarine-launched ballistic missiles (SLBM) on parade with tanks and other heavy machinery in front of Kim Jong Un.
Local authorities said further analysis would be required to determine conclusively whether the missile in the tubes was an ICBM.
The statement Sunday said it wasn't clear what kind of missile was involved.