Sheikh Mohamed bin Zayed, Crown Prince of Abu Dhabi and Deputy Supreme Commander of the UAE Armed Forces, joined world leaders in wishing Japanese Prime Minister Shinzo Abe a rapid recovery and praised his contributions to bilateral relations during his years as Japan's longest-serving leader. Mr Abe announced Friday that he is stepping down because of a health problem. He is expected to stay on until a new governing party leader is elected and formally approved by the parliament. Here are some other reactions from around the world. President Donald Trump said he was surprised by Mr Abe's stepping down and paid his "highest respect to ... a very, a great friend of mine." Speaking to reporters aboard Air Force One, Trump said, "We had a great relationship. And I just feel very bad for him. Because it must be very severe. Look, for him to leave - he loves his country so much and for him to leave, I just can't imagine what it is. He's a great gentleman and so I'm just paying my highest respect." UN Secretary-General Antonio Guterres' spokesman said he wishes Abe a full recovery and salutes "the prime minister's distinguished career ... and his consistent and constructive engagement with the UN to address global challenges." The UN chief "had a very productive relationship with prime minister Abe," spokesman Stephane Dujarric said, pointing to their close work on a number of issues especially universal health care initiatives. South Korean President Moon Jae-in's office said Mr Abe dedicated many years to the development of bilateral relations and achieved "various meaningful accomplishments" as Japan's longest-serving prime minister. It said Seoul will continue to work with Tokyo's next prime minister and Cabinet to promote "friendship and cooperation" between the countries. Relations between South Korea and Japan sank last year to their lowest point in decades as they feuded over trade issues, wartime history and military cooperation. Longtime German Chancellor Angela Merkel, who worked with Mr Abe during both of his spells in office, sent him a message saying he was "always a constructive and reliable partner in our common commitment to multilateralism, free trade, peaceful conflict resolution and rules-based order." "For the future, I wish you a swift and complete recovery and personal well-being," she wrote. Prime Minister Scott Morrison paid tribute to Shinzo Abe as "Australia's true friend" and said that he would like to thank Abe for his enduring commitment to Australia-Japan relations over a long and successful career. Morrison said Australia and Japan shared a vision for an open, peaceful and prosperous Indo-Pacific region. "Prime Minister Abe is a man of integrity and wisdom," Mr Morrison said. "He has been the senior statesman in our region and across the globe, a strong promoter of open trade and an outstanding international diplomat for Japan." Taiwanese President Tsai Ing-wen said Mr Abe "has always been very friendly to Taiwan. He has always been very positive, no matter it be his policies or his feelings toward Taiwanese people. We cherish the friendship he has for Taiwan. We also wish him good health." Chinese foreign ministry spokesperson Zhao Lijian declined to comment directly on Mr Abe's health, saying it was Japan's internal affair. However, he added that "China and Japan are close neighbors. We are willing to work with Japan to jointly press ahead with continuous improvement and development of China-Japan relations." Foreign Secretary Dominic Raab paid tribute to "the great things" that Mr Abe has achieved, and said he "leaves a strengthened UK-Japanese friendship, which we look forward to continuing in the years ahead. I wish him well for the future." Philippine Foreign Secretary Teodoro Locsin Jr described Mr Abe as Japan's "greatest postwar PM (prime minister)" in a tweet. He said Philippine President Rodrigo Duterte and Abe had a frank relationship. "Watching President Duterte and PM Abe talking was like watching two old friends, no holds barred, talking frankly and freely of the true lay of the land and what can and cannot be done," Locsin said. IOC President Thomas Bach credited Abe with the return of the Olympics to Japan after the 1964 Tokyo Olympics, 1972 Sapporo Winter Olympics and 1998 Nagano Winter Olympics. "All the Japanese athletes and the athletes of the entire world are very grateful to him," Bach said. The Olympics were to be held in Tokyo this year, but they were postponed a year because of the coronavirus. John Coates of the Australian Olympic Committee and chair of the Tokyo 2020 Coordination Commission, said in a statement Saturday that Mr Abe stepping down was "disappointing news from a professional and personal perspective. My interactions with him have always been very positive and constructive. I certainly hope he can successfully overcome the current challenges he faces away from political office. I very much look forward to PM Abe joining us for the Opening Ceremony on 23 July 2021 in the new National Stadium that he was instrumental in delivering. His support has been enormous."