North Korea boasted it is in the final stages of enriching uraninum on Friday, a process that could give the rogue nation a second way to make a nuclear bomb.
The official Korean Central News Agency said in a report early Friday that North Korea sent a letter to the U.N. Security Council outlining its moves.
"Uranium enrichment tests have been successfully carried out and that process is in the concluding stage," the letters was quoted by Reuters through the KCNA official.
"We are prepared for both sanctions and dialogue," Reuters reported the letter as stating.
The U.N. Security Council has tightened sanctions against North Korea for a series of nuclear provocations, including an underground atomic test.
The dispatch said plutonium "is being weaponized," and that uranium enrichment — a program North Korea revealed in recent months — was entering the "completion phase." Experts had long suspected the existence of a hidden uranium enrichment program, which would give the regime a second source of nuclear material.
North Korea called the decision to push ahead with its nuclear programs a reaction to the Security Council's moves to tighten sanctions against the regime for testing a nuclear bomb in May. The report called the resolution a "wanton violation of the DPRK's sovereignty and dignity." DPRK stands for the country's official name, the Democratic People's Republic of Korea.
The U.S., China, Japan, Russia and South Korea have been negotiating with North Korea for years on dismantling its nuclear program in exchange for aid and other concessions.
North Korea walked away from the talks earlier this year.
The Associated Press contributed to this report.