SEOUL North Korea's Kim Yo Jong, sister of leader Kim Jong Un, said on Monday that the United States should avoid any "foolish act" that could put its security at risk and rejected offers of talks as a ploy, state media KCNA news agency reported.

Kim made her comments after White House National Security Adviser Jake Sullivan said the United States remains concerned that North Korea would carry out another intercontinental ballistic missile (ICBM) test, after it last week fired an ICBM off its east coast.

"The United States should stop a foolish act that could put its security at risk by provoking us," Kim said in a statement carried by KCNA.

She criticised U.S. plans for a nuclear-armed ballistic missile submarine to visit South Korea and said that such efforts to increase "extended deterrence" would only push Pyongyang further from the negotiating table.

Kim also rejected U.S. calls for unconditional talks and said that Washington is wrong if it believes North Korea's disarmament was possible.

"The United States is being delusional if it believed that it could stop our advancement and achieve irreversible disarmament by temporarily halting joint military drills, deployment of strategic assets or easing of sanctions," she said.

North Korea has in recent days accused American spy planes of flying over its exclusive economic zone, condemned a recent visit to South Korea by an American nuclear-powered cruise missile submarine, and vowed to take steps in reaction.

(Reporting by Heekyong Yang; Editing by Angus MacSwan, David Holmes and Mike Harrison)