McMaster was speaking hours after US and South Korean defense officials told CNN that an attempted missile launch by North Korea failed.
Pence, addressing an Easter service with American troops in South Korea, said the US commitment to South Korea was unwavering.
Referring to the display of intercontinental ballistic missile by North Korea during a recent parade, the US National Security Advisor said the objective of that parade is to demonstrate military prowess in a threatening way.
"I think deeper down it is a learning curve, it's very hard - the situation in North Korea - and it's perplexed administration after administration", Nakamura said.
Recent satellite images suggest its main nuclear site is "primed and ready", according to specialist USA website 38North.
Despite Mr Trump's remarks China, North Korea's ally and neighbour, has warned of the possibility of war "at any time". Later, McMaster said, "it's time for us to undertake all actions we can, short of a military option, to try to resolve this peacefully".
The United States has about 28,500 troops and equipment stationed in the South, mostly stationed at the demilitarised zone (DMZ) at the 38th parallel dividing the Korean Peninsula into North and South.
"The type of missile is still being assessed", the U.S. Pacific Command says in an emailed statement.
Hours later U.S. Vice President Mike Pence landed in South Korea for talks on the North's increasingly defiant arms program. In an interview with The Associated Press, a senior North Korean official said Friday that Pyongyang has determined that Trump is "more vicious and aggressive" than his predecessor, Barack Obama.
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Despite those measures, "most analysts agree that U.S. and multilateral sanctions have not prevented North Korea from advancing its fledgling nuclear weapons capability", said a report past year from the U.S. Congressional Research Service.
Some outlets have reported that the US may have conducted a cyber-attack that affected the North Korean missile program - a tactic the Obama administration reportedly used on several occasions.
The Trump administration has not indicated publicly it is interested in reviving moribund diplomatic negotiations with North Korea over its nuclear and missile programs.
It also comes amid mounting tensions on the peninsula that led Beijing to warn last week a "storm is about to break" because of rising brinkmanship with Washington over Pyongyang's nuclear programme.
At the same it's increased its military footprint in the region by deploying a naval carrier strike group to waters off the Korean Peninsula. That launch came shortly before Trump's first meeting with Chinese leader Xi Jinping. North Korea unveiled its latest submarine-launched ballistic missile and a version of the same missile that can be launched from land-based launchers - both of which use solid fuel and present a far greater challenge to find and destroy before they're fired off.
More directly on North Korea, the president returned to a theme of placing much onus on China for reining in the North.
The parade was attended by the North's young leader Kim Jong-un, grandson of Kim Il-sung, who is known as the Dear Leader in the Kim dynasty.
Six-nation negotiations on dismantling North Korea's nuclear program in exchange for aid fell apart in early 2009.
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