(Adds call by U.N. Millennium Campaign)
By Patrick Worsnip
UNITED NATIONS, Nov 13 (Reuters) - U.N. Secretary-General Ban Ki-moon has appealed to leaders meeting at a financial summit in Washington this weekend not to let the global crisis become a "human tragedy" for people in poor countries.
In a letter to leaders of the G20 -- the Group of Seven top industrial democracies and other key economies -- Ban warned that throwing hundreds of millions of people out of work could have major political and security implications.
"The poorest and most vulnerable everywhere, but particularly in the developing countries, will be the most affected" by the world growth slowdown now being predicted, he said in the letter released by the United Nations on Thursday.
"We need most of all to join forces to take immediate action to prevent the financial crisis from becoming a human tragedy."
Ban, who will attend the Washington meeting, said he would try to speak for the more than 170 countries that will not be represented there.
"If hundreds of millions of people lose their livelihoods and their hopes for the future are dashed because of a crisis they have absolutely no responsibility for, the human crisis will not remain just economic," the U.N. chief said.
"It will assume new and difficult political and security dimensions that could overwhelm the ones we are already facing."
Ban urged that the meeting "show solidarity toward the neediest" and called on the wealthy countries to maintain aid commitments they had made before the global credit crisis, sparked by a U.S. mortgage crunch, struck in September.
Institutional reforms could not be restricted to financial sector regulation and also must deal with broader challenges such as climate change, conflict prevention and eradication of poverty.
Investing in new technologies and "green jobs" to combat climate change would both fight the short-term crisis and lay the foundation for long-term growth, said Ban, who has made the environment a central plank of his policy.
He also called on countries to resist protectionism and quickly resolve issues holding up the Doha trade round.
Separately, the U.N. Millennium Campaign called on the G20 summit to assign $300 billion in extra aid and debt relief to poor countries, to make up for gross domestic product it said they would lose because of the crisis over the next two years.
The campaign was set up by Ban's predecessor, Kofi Annan, in 2002 to press for governments to achieve the Millennium Development Goals -- a set of U.N. targets for slashing poverty, hunger and disease by 2015. (Editing by Bill Trott)