United Nations Secretary General Ban Ki-moon has asked G-20 leaders, gathering in Washington this weekend to attend a summit on global market meltdown, to take immediate action to prevent the current financial crisis from turning into a 'human tragedy.'

In a letter to the leaders on Thursday, he warned that unless steps were taken the 'human tragedy' could result in new political and security challenges overwhelming the current economic crisis.

Ban's letter has been released at a time when outgoing US President George W Bush is seeking to lower the expectations from the high-level meeting, saying the crisis is so deep that it could not be resolved in one single meeting and several such gatherings might be needed.

Emphasising on the role of financial experts, he said that the leaders would have to prepare recommendations with the help of experts but no time frame was given. Analysts said it could be a time consuming process.

Bush also called for reform of international financial institutions, including the World Bank and the International onetary Fund but analysts said it too could be a long-drawn process as position of the incoming US administration was unclear.

An area which could see differences at the meeting, they say, is Bush's views on market regulation which the American President would like to keep to the minimum. 

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.

This is also 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," Ban said in the letter.

"An important way of doing this will be by meeting the existing commitments on aid, so that progress towards the Millennium Development Goals can be maintained," he added, referring to the internationally agreed targets to halve extreme poverty and other ills by 2015.

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," Ban said in the letter.

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 changes, he said, could only be met through a 'reinvigorated and inclusive multilateralism.'

The United Nations has much to contribute and remains the anchor of such a system, he added.

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