UNITED NATIONS, Sept 21 (Reuters) - The Taliban have asked to address world leaders at the United Nations in New York this week and nominated their Doha-based spokesman Suhail Shaheen as Afghanistan"s U.N. ambassador, according to a letter seen by Reuters on Tuesday. Taliban Foreign Minister Amir Khan Muttaqi made the request in a letter to U.N. Secretary-General Antonio Guterres on Monday. Muttaqi asked to speak during the annual high-level meeting of the General Assembly, which finishes on Monday. Guterres" spokesperson, Farhan Haq, confirmed Muttaqi"s letter. The move sets up a showdown with Ghulam Isaczai, the U.N. ambassador in New York representing Afghanistan"s government ousted last month by the Taliban. Haq said the rival requests for Afghanistan"s U.N. seat had been sent to a nine-member credentials committee, whose members include the United States, China and Russia. The committee is unlikely to meet on the issue before Monday, so it is doubtful that the Taliban foreign minister will address the world body. Eventual U.N. acceptance of the ambassador of the Taliban would be an important step in the hardline Islamist group"s bid for international recognition, which could help unlock badly needed funds for the cash-strapped Afghan economy. Guterres has said that the Taliban"s desire for international recognition is the only leverage other countries have to press for inclusive government and respect for rights, particularly for women, in Afghanistan. The Taliban letter said Isaczai"s mission "is considered over and that he no longer represents Afghanistan," said Haq. Until a decision is made by the credentials committee Isaczai will remain in the seat, according to the General Assembly rules. He is currently scheduled to address the final day of the meeting on Sept. 27, but it was not immediately clear if any countries might object in the wake of the Taliban letter. The committee traditionally meets in October or November to assess the credentials of all U.N. members before submitting a report for General Assembly approval before the end of the year. The committee and General Assembly usually operate by consensus on credentials, diplomats said. Others members of the committee are the Bahamas, Bhutan, Chile, Namibia, Sierra Leone and Sweden. When the Taliban last ruled between 1996 and 2001 the ambassador of the Afghan government they toppled remained the U.N. representative after the credentials committee deferred its decision on rival claims to the seat. The decision was postponed "on the understanding that the current representatives of Afghanistan accredited to the United Nations would continue to participate in the work of the General Assembly," according to the committee report.