This will be the first time that the G-20 summit - aimed at promoting dialogue between advanced and emerging countries on key issues regarding economic growth and stability of the financial system - has met at the level of heads of State, as well as the first time that the United Nations Secretary-General has been invited to attend.
"It is essential that the G-20 meeting signals an unmistakable common resolve to overcome the crisis, to act together, to act with urgency and to show solidarity towards the neediest," Mr. Ban said in a letter to the global leaders attending Saturday's meeting in Washington, D.C.
"An important way of doing this will be by meeting the existing commitments on aid, so that progress towards the Millennium Development Goals (MDGs) can be maintained," he added, referring to the internationally agreed targets to halve extreme poverty and other ills by 2015.
Mr. Ban stressed that institutional reforms cannot be restricted to financial sector regulation, but must deal with the broader challenges for human security, including climate change, conflict prevention and the eradication of poverty.
He noted that an opportunity for climate change exists in the fiscal stimulus packages many countries are introducing as the economic crisis requires an increase in public investment to shore up national markets.
"To limit climate change successfully we will need to invest in new technologies, in green jobs and in helping the world cope with the changes that are already inevitable," Mr. Ban said in the letter.
"Targeting a substantial part of the needed public spending to these needs will help fight the short-term crisis, while laying the foundation for the long-term sustainability of economic growth."
The Secretary-General also pointed to the lessons learnt from the economic depression of the 1930s, noting that greater protectionism at the expense of trade can deepen a recession, and that trade restrictions undermine jobs in the aggregate.
"An early resolution of the issues holding up the Doha trade round [aimed at promoting free-trade] would be a great contribution to overcoming the crisis," he said.
"These broad challenges can only be met through a reinvigorated and inclusive multilateralism. The United Nations has much to contribute and remains the anchor of such a system."