Speaking with Aso, Ban said he would mobilise "every effort" to reach an agreement to adopt an ambitious global treaty to replace the Kyoto protocol, which expires in
"We know the answer. We must take the course of sustainable green growth"
"We know the answer. We must take the course of sustainable green growth," Ban said, urging Japanese business leaders to join the fight against global warming.
Aso, for his part, said Japan was ready to "play an aggressive leadership role" at the Copenhagen meeting.
Japan, the world's fifth-largest greenhouse gas emitter, announced in June a new target to cut its emissions 15 percent from its 2005 level by 2020.
Aso said the new target matches the levels pledged by the European Union and the United States.
The UN secretary general is in Japan at the start of a three-nation Asian tour that will take him on to Singapore and then to Myanmar, where he is due to hold talks with the country's military leaders.
Ban has said he will use his visit to Myanmar to convey international concerns over the political situation in the country, including the trial of detained opposition leader Aung San Suu Kyi.