(Adds details, Malpass comments) LONDON, April 9 (Reuters) - Private sector creditors do not expect to be significantly affected by the latest extension of the G20 Debt Service Suspension Initiative (DSSI), the Institute of International Finance (IIF) said on Friday. In a letter sent to the G20 group of major governments during the Spring meetings of the International Monetary Fund and World Bank, the IIF said more coordination between various creditors was needed as part of efforts to help the poorest nations tackle their debt burdens. “Given the diversity of creditors and debt instruments — and heightened risks for debt sustainability in some countries — an appropriate forum for creditor coordination is urgently needed,” the group said in the letter. World finance chiefs agreed on Wednesday to boost reserves at the International Monetary Fund by $650 billion and extend a debt-servicing freeze to help developing countries deal with the coronavirus pandemic. World Bank President David Malpass said earlier this week that the DSSI extension would likely be the “last or final” one. The move could entice countries to move towards the G20’s so-called “Common Framework”, under which countries could fully restructure debts rather than just postpone payments for a year or two under the DSSI. The Common Framework also pushes for restructuring debts with the private sector, making it a hurdle for some borrowing countries that could see their credit ratings lowered, thus raising their financing costs. Malpass has spearheaded a push to get private creditors involved in the debt relief initiatives. (Reporting by Karin Strohecker; Editing by Tom Arnold and Andrea Ricci)