In a report published on North Korean state media KCNA, the spokesman said his country had nothing to do with terrorism, saying the relisting was an "absurdity."
"This is a serious provocation and a violent infringement upon our dignified country," the spokesman said according to KCNA.
The Trump administration announced on Monday that North Korea would again be included on the list of states which sponsor terrorism, adding the US Treasury Department would be initiating further sanctions on the already isolated nation.
"Today the United States is designating North Korea as a state sponsor of terrorism. Should have happened a long time ago. Should have happened years ago," President Donald Trump said.
Former President George W. Bush removed North Korea from the list in 2008.
It marked another escalation in the war of words between Washington and Pyongyang over the latter's ongoing nuclear ambitions, which include developing a missile which would have the ability to strike the US capitol.
Trump has pushed hard for North Korean leader Kim Jong Un to halt his nuclear program, but so far Pyongyang has refused to even consider abandoning its weapons development.
On Tuesday, the US placed new sanctions on one individual, 13 companies and 20 vessels which all engage in millions of dollars worth of trade with North Korea.
"We are steadfast in our determination to maximize economic pressure to isolate (North Korea) from outside sources of trade and revenue," US Treasury Secretary Steven Mnuchin said in a statement.
But the North Korean Foreign Ministry spokesman was defiant in the face of the new measures, saying they would "keep the treasured nuclear sword in (their) hands more tightly."
"No sanction or pressure can stand up to the great and limitless strength of self-reliance and self-development of our people who are closely rallied around their leader," the North Korean foreign ministry spokesman said, according to KCNA.
Seoul: Korean war armistice violated
The new sanctions and North Korea's defiant response come amid complaints from South Korea that their northern neighbor violated the Korean War armistice agreement in the past week.
North Korean soldiers attempting to catch a defector making a break across the demilitarized zone (DMZ) on November 13 fired into South Korea, while one soldier even crossed the border.
The defector was shot about five times and badly injured, but emergency medical treatment in South Korea has helped stabilize his condition.
The war between North Korea and South Korea never officially ended but an armistice has remained in place between the two countries since 1953.
According to a document from the South Korean Joint Chiefs of Staff, North Korea has been accused of defying the armistice thousands of times since 1953, though not all the violations are nearly as dramatic as a shootout caught on camera.
North Korea claims in response the South has also breached the armistice thousands of times.