North Korea has said it needs the capability to launch intercontinental missiles at the heart of the United States to prevent an invasion.
The North is ready to give the United States a "severe lesson" with its strategic nuclear force if it takes military action against it, it said in a statement to a regional meeting in Manila.
In a transcript of a statement by the North's foreign minister, Ri Yong-ho, Pyongyang called new UN sanctions "fabricated" and warned there would be "strong follow-up measures" and acts of justice.
"We will under no circumstances put the nukes and ballistic rockets on the negotiating table," Mr Ri said.
The statement said the North's intercontinental ballistic missile tests in July proved that the entire United States was in its firing range, and those missiles were a legitimate means of self-defence.
Mr Ri also said that his country has no intention of using nuclear weapons against any country "except the US".
He said the only way that would change is if another country joined in an American action against North Korea.
Earlier, North Korea warned it would launch a "thousands-fold" revenge against the United States after it introduced tough new UN sanctions.
The UN Security Council unanimously approved new penalties for the North after its recent test launches of several intercontinental ballistic missiles.
The US-drafted resolution bans North Korean exports of coal, iron, iron ore, lead, lead ore and seafood and is aimed to pressuring Pyongyang to end its nuclear programme.
It also prohibits countries from increasing the current numbers of North Korean labourers working abroad, bans new joint ventures with North Korea and any new investment in current joint ventures.
