UNITED NATIONS - Chief executives from the world's leading businesses have called on the United Nations to strengthen the UN Convention against Corruption. In a letter to UN Secretary-General Ban Ki-moon released Thursday, the CEOs said the world's only anti-corruption instrument was an effective start to combating corruption but it needed to go further by establishing a review mechanism at the next Conference of State Parties to be held in Doha in November. "Especially now, in a period of deep financial and economic turmoil, an effective implementation review mechanism is essential," said the letter. "The economic crisis will inevitably place severe strains of worldwide competition, threatening an erosion of ethical standards that will be hard to reverse." The UN convention, which was adopted in 2003, has been signed by 140 countries and ratified by 136. Designed to curb corruption in the public and private sectors, the convention contains preventative measures as well as law enforcement provisions. "I deeply appreciate the leadership demonstrated by the corporate community in this critical matter," said Ban in response to the letter. "I very much hope that (the CEO's) letter will be an encouragement to successfully establishing a review mechanism." Since 2006, parties to the convention have been trying to establish an effective and efficient review process but disagreements over organizing such mechanisms have stalled any progress. In their letter, the CEOs recommend that the review process should have adequate and dependable long-term funding, establish country visits with peer reviewers from other countries, and should be transparent with published reports. The letter came from the largest business organizations in the world-- the International Chamber of Commerce, Transparency International, the United Nations Global Compact, and the World Economic Forum Partnering Against Corruption Initiative.