The protocol left several issues open to be decided later by the sixth Conference of Parties COP6 of the UNFCCC, which attempted to resolve these issues at its meeting in the Hague in late 2000, but it was unable to reach an agreement due to disputes between the European Union (who favoured a tougher implementation) and the United States, Canada, Japan and Australia (who wanted the agreement to be less demanding and more flexible).
COP6 sa v roku 2000 pokúšala vyriešiť tieto otázky na stretnutí v Hágu, ale nebola schopná dosiahnuť dohodu kvôli sporom medzi Európskou úniou na jednej strane (ktorá presadzovala tvrdšiu dohodu) a USA, Kanadou, Japonskom a Austráliou a inými na druhej strane (ktoré chceli aby dohoda bola menej náročná a flexibilnejšia).