The U.S. and North Korea went back and forth at the U.N. about the legality of Pyongyang’s recent spy satellite launch on Monday, an interaction that one source described as perhaps the lengthiest diplomatic dialogue between the two countries in years.

The exchange took place during an open meeting of the U.N. Security Council (UNSC) on North Korea’s satellite launch, where a long-running impasse between permanent members that has hindered the passage of new sanctions continued.