U.N. Secretary-General Ban Ki-moon says he expects robust agreement at the Copenhagen climate change summit, which will open next week.

He made the statement to reporters at the U.N. headquarters in New York Thursday as he expressed hope that next week’s summit would yield an agreement on the reduction of greenhouse gas levels. He also expressed hope that advanced countries would support developing countries in efforts to fight climate change.

Ban also said he was determined to set a six-month deadline for any deal agreed upon in Copenhagen to be given the full force of international law.

Ban also admitted that there were “trust issues” between advanced and developing countries over climate change. He said difficulty is expected in coordinating views on reducing greenhouse gas emission levels, as advanced countries are unveiling related plans in accordance with their local situations.