The special climate change meeting in New York comes before the General Assembly meeting on Tuesday.
Items on the agenda for the assembly include the conflict in Sudan's Darfur region, where Ban hopes that a joint UN-African Union peacekeeping force will be able to deploy effectively, and the nuclear programmes of Iran and North Korea.
Monday's climate change meeting, the first ever held at the UN, comes amid concerns that rising global temperatures are melting the Arctic, leading sea levels to rise.
The meeting is also set to hear from world leaders such as Angela Merkel, Germany’s chancellor, and Nicolas Sarkozy, the French president.
|Watch Laura Kyle's report on why credits are sought to protect rainforests|
Arnold Schwarzenegger, the Republican governor for California in the US, is due to talk at the meeting.
Schwarzenegger and the Democrat-led legislature last year approved a law requiring California's industries to reduce emissions of greenhouse gases by an estimated 25 per cent by 2020.
The law was opposed by the US Republican administration, which has resisted limits on emissions so far.
"California is moving the United States beyond debate and doubt to action," he says in remarks prepared for the meeting.
Also speaking at the summit, Rajendra Pachauri, chief UN climate scientist, says there is now "much greater evidence of human influence on climate change," and that "it's time for action".
Concern over US role
The meeting comes ahead of an annual climate treaty conference in Bali, Indonesia.
That forum will bring European nations, and Japan among others together to begin discussions towards an emissions-reduction agreement to succeed the 1997 Kyoto pact.
The US rejects the Kyoto protocol, which requires 36 industrial nations to reduce greenhouse emissions from industry, agriculture and transport by an average of five per cent below 1990 levels by 2012.
The European Union (EU) has committed to reduce emissions by at least an additional 20 per cent by 2020, but concerns remain that without US co-operation, any plan will be extremely limited in its effectiveness.
George Bush, the US president, who has opposed negotiated limits on gases, will not take part in Monday's meeting. He is due to attend a small dinner after the summit, joining a gathering of key leaders hosted by Ban.
Also at Monday's meeting, Indonesia will lead a group of about 20 nations, called the Forestry 8, which will call for financial compensation if members of the group take action to preserve their rainforests.
The group, which has swelled to 20 members from the original eight, collectively hold more than 80 per cent of the world's rainforests, which store vast quantities of carbon.
The Kyoto treaty, which aims to cut the world's emissions, only recognises and rewards re-planting trees, or converting open land into forests.
However, rainforest nations want incentives not to cut down their forests in the first place.