Former U.S. Vice President Joe Biden on Tuesday said he would not meet with North Korean leader Kim Jong Un — who once lambasted Biden as a rabid dog — without "preconditions," as President Donald Trump has done three times.

Biden, asked at the evening's Democratic presidential debate in Iowa if he was willing to sit down for talks with the leader of the nuclear-armed country, said Trump's meetings with Kim had been a gift to the young dictator, bestowing him with a sense of "legitimacy."

The former senator and vice president said the meetings had weakened crushing economic sanctions against the country that many experts believe brought Kim to the negotiating table in the first place.