North Korea's U.N. ambassador is accusing the United States of imposing "an economic blockade" on his country and deploying nuclear assets on the Korean peninsula aimed at toppling leader Kim Jong Un.

Ja Song Nam said Tuesday the U.S. push for countries to implement what he called "illegal and unjustifiable" U.N. sanctions on North Korea are part of America's "frantic attempt to completely block our peaceful economy."

The ambassador told the General Assembly committee dealing with economic and financial issues that "the U.S. is clinging to unprecedented nuclear threats and blackmail, economic sanctions and blockade to deny our rights to existence and development, but they only result in our sharper vigilance and greater courage."

The U.N. Security Council has imposed the toughest sanctions ever on North Korea.