The Foreign Ministry of the Democratic People's Republic of Korea (DPRK) issued a memorandum on the nuclear issue of the Korean Peninsula, the official Korean Central News Agency (KCNA) reported Wednesday.

The memorandum said the denuclearization of the Korean Peninsula is the invariable stand of the DPRK, but confidence-building is the premise, noting that it was the U.S. that introduced nuclear weapons into the Korean Peninsula for the first time.

It said the DPRK once worked hard to establish a nuclear-free zone through peaceful dialogue and negotiation. However, those efforts proved invalid. The DPRK was forced to "deter the U.S. nukes with its own nukes, not making a verbal appeal only."

According to the document, the nuclear weapons deployed by the U.S. in South Korea steadily increased from the 1950s to the 1970s.

The DPRK will join "the international nuclear disarmament effort with an equal stand with other nuclear weapons states," the memorandum said.

In the recent "Nuclear Posture Review," the Obama administration failed to rule out the use of nuclear weapons against countries like the DPRK and Iran, which it said violate and quit the Nuclear Non-Proliferation Treaty (NPT).

In a statement released April 9, a spokesman for the DPRK Foreign Ministry denounced the "Nuclear Posture Review" as pouring cold water on restoring six-nation talks.

The spokesman said the DPRK developed nuclear weapons for the purpose of "deterring the U.S. attack and defending its sovereignty and right to existence." The country has so far "sincerely implemented its international obligation as a responsible nuclear weapons state."

The DPRK withdrew from the NPT on Jan. 10, 2003.