Pyongyang would have to "reconsider the major steps we have taken so far," a North Korean diplomat in Geneva said.
North Korea on Tuesday accused the United States of "inciting tension" by holding joint military exercises with South Korea and said Pyongyang would take measures to defend itself.
Ju Yong Chol, a North Korean diplomat in Geneva, told the U.N.-sponsored Conference on Disarmament that Pyongyang would have to "reconsider the major steps we have taken so far." He did not mention its latest firing of missiles into the sea off its east coast earlier on Tuesday.
Pyongyang also warned that hostile moves against it "have reached the danger line."
North Korea fired the missiles into the sea off its east coast for the fourth time in less than two weeks, South Korea said on Tuesday.
The North, criticizing the U.S.-South Korean drills and their use of high-tech weapons, has fired a series of missiles and rockets since its leader Kim Jong Un and U.S. President Donald Trump agreed at a June 30 meetingto revive stalled denuclearization talks.
North Korea has said it is committed to diplomacy and it will wait until the end of the year for the United States to soften its policy of sanctions and political pressure over Pyongyang's nuclear weapons and ballistic missile programs.
But if Washington and Seoul disregard North Korea's repeated warnings, "we will make them pay (a) heavy price," a North Korean foreign ministry spokesman said in a statement released through state news agency KCNA.
Trump has played down the tests by saying they did not break any agreement he had with Kim but the talks have yet to resume.
South Korea's Joint Chiefs of Staff said what appeared to be two short-range ballistic missiles were fired from near Kwail on North Korea's west coast, about 80 miles southwest of Pyongyang, in South Hwanghae province early on Tuesday.
They were the fourth set of launches since July 25.
South Korea's defense ministry said on Tuesday the missile launch went against the spirit of easing tension on the Korean peninsula.
A United Nations report said on Monday Pyongyang has continued to enhance its nuclear and missile programs and used cyberattacks to take in $2 billion to fund the development.