UN Secretary-General Ban Ki-moon declined an appeal Wednesday by 112 former presidents and prime ministers from around the world to return to Myanmar and press for the release of all political prisoners there. In an effort led by Norway's former prime minister Kjell Magne Bondevik, the former leaders urged Ban to make good on the Security Council's call in October 2007 for Myanmar to release the prisoners, including Nobel Peace Prize winner Aung San Suu Kyi. They wrote that Ban should return to Myanmar because it "would illustrate for the world whether or not the Burmese military regime is serious about making changes called for by the United Nations Security Council and your good offices." Ban traveled to Myanmar, also known as Burma, in May in the wake of Cyclone Nargis. Setting aside political considerations, he gambled correctly that a private meeting with Senior Gen. Than Shwe would persuade Myanmar's reclusive leader to ease access for foreign aid workers and relief supplies. Ban, who had considered returning this year, received the letter and spoke with Bondevik on Wednesday. "He said he would like to visit Myanmar again to discuss a broad range of issues but that he will not be able to do so without reasonable expectations of a meaningful outcome," U.N. spokeswoman Michele Montas said. Ban's special envoy to Myanmar, Ibrahim Gambari, also will not return again until he has a "real possibility of moving forward there," she added. Among the other signers of the letter were former U.S. presidents George H.W. Bush and Jimmy Carter, former British prime ministers Tony Blair, Margaret Thatcher and John Major, former Soviet leader Mikhail Gorbachev, former Japanese prime minister Junichiro Koizumi and former Polish president Lech Walesa. "We urge you to make it clear that all political prisoners in Burma must be released by the end of this year, regardless of whether you travel to Burma," they wrote. The letter was released by Bondevik's Oslo Center for Peace and Human Rights and by a Washington area-based advocacy group, Freedom Now. Myanmar's military, which has held power since 1962, tolerates no dissent. It has further ramped up its crackdown on dissent since Buddhist monks led pro-democracy protests in September 2007. The government holds more than 2,100 political prisoners, up sharply from nearly 1,200 in June 2007, before the demonstrations, according to international human rights groups.