In an interview with the BBC on Monday, Vice Foreign Minister Han Song-Ryol said, "We'll be conducting more missile tests on a weekly, monthly and yearly basis".
Pyongyang insists it needs a powerful arsenal - including atomic weapons - to protect itself from what it says is the ever-present threat of invasion by hostile U.S. forces.
It was the first time that Kim has personally criticised Washington's military action, and the message - published by North Korea's state-run news agency KCNA - came on the same day as US Vice President Mike Pence's statement warning Pyongyang against putting to test the US resolve as made evident in recent bombings in Syria and Afghanistan, Efe news reported.
South Korea, which accuses China or discriminating against some South Korean companies working in China, and the United States say the sole objective of THAAD is to guard against North Korean missiles.
Trump wrote Sunday on Twitter that China was working with the United States on "the North Korea problem".
Vice President Mike Pence warned in Seoul today that North Korea "would do well not to test" the "resolve" of President Trump, "or the strength of the Armed Forces of the United States in this region".
North Korean Leader Kim Jong Un observes a target-striking contest by the Korean People's Army (KPA). -South Korean military exercises being staged now are the largest-ever "aggressive war drill".
One of the great worries associated with taking action against North Korea would be the ability of the Kim regime to retaliate against South Korea.
North Korean Deputy Ambassador to the United Nations Kim In Ryong meanwhile told a news confernece in NY that the hermit kingdom was ready for "any mode of war", saying that North Korea would respond to a missile or nuclear strike "in kind".
Kim In Ryong told a news conference that "if the US dares opt for a military action", North Korea "is ready to react to any mode of war desired by the U.S".
"The era of "strategic patience" is over", he said, echoing similar comments by Secretary of State Rex Tillerson last month.
The Trump administration is hoping that China will help rein in North Korea in exchange for other considerations.
North Korea has defied repeated economic sanctions and global pressure over its nuclear regime, which saw it carry out two tests in 2016 and one so far this year, and has vowed a "merciless response" to any United States provocation.
The BBC's Stephen Evans in Seoul says United States policy now seems to be to persuade China to contain North Korea while keeping the economic and military pressure on.
Sin warned that "if we notice any sign of assault on our sovereignty, our army will launch merciless military strikes against the USA aggressors, wherever they may exist, from the remote USA lands to the American military bases on the Korean Peninsula, such as those of Japan and elsewhere".
The good news is that war didn't break out on the Korean peninsula over the weekend.
Foreign companies bringing tour groups to North Korea, however, have seen no dip in demand.
In Moscow, Russian Foreign Minister Sergey Lavrov, speaking to reporters Monday evening, said he hoped there would be "no unilateral actions like those we saw recently in Syria and that the USA will follow the line that President Trump repeatedly voiced during the election campaign".