The remarks come as US President Donald Trump has renewed overtures to North Korean leader Kim Jong-un, expressing interest in another meeting and saying this month that Kim had responded to his outreach.
Analysts say Pyongyang has shown little official willingness to resume talks.
"We once again and clearly recognised the expression of the US open attitude to be always hostile to the DPRK," a ministry spokesperson said in remarks carried by KCNA on Thursday.
DPRK stands for the Democratic People's Republic of Korea, the North's official name.
The spokesperson was responding to the US State Department's approval of a potential sale to South Korea of $US125 million ($A174 million) worth of AIM-9X Sidewinder air-to-air tactical missiles and related equipment, which Pyongyang said posed "a new threat" to its security environment.
North Korea also criticised a US plan to fund activities related to documenting its human rights situation and gathering information on the country, describing the efforts as part of a campaign aimed at creating instability in its social system.
The spokesperson said Washington had this year approved sales to South Korea of various weapons systems, including advanced air-to-air missiles, naval helicopters, attack helicopters and precision-guided bombs, while encouraging Seoul to boost its war-fighting capabilities.
"Now that the military integration of the US and its allies is being accelerated in the Asia-Pacific region, we cannot overlook the adverse effect of the US sale of its weapons to the ROK on the regional security environment," the spokesperson said, using the acronym for South Korea's official name, the Republic of Korea.
North Korea was aware of such threats and would have a "serious, immediate and powerful response" to hostile acts in different spheres, the official said.
