The United States national wrestling team will not visit Iran later this month for an international tournament in a decision believed to be the result of political tension between the two countries, the sports daily Iran reported Thursday.    No specific reasons have been given for the U.S. team's decision not to take part in the annual International Takhti Wrestling Cup - named after the late Iranian world wrestling champion Gholam-Reza Takhti - to be held in Teheran between February 20 and 22. The decision is believed to have been made by the American side, the report said.    The U.S. State Department had called on American citizens not to travel to Iran after the inclusion of Iran by U.S. President George W. Bush into the "axis of evil" and speculation that Iran might be one of the next American targets in the anti-terrorism campaign.    The U.S. wrestling team attended the same games in January 2000 as a sign of improvement between the two political foes which have had no ties for over two decades.    The state-run Iranian television IRIB harshly criticised Wednesday the U.S. network NBC which, during the marching in of the Iranian team at the opening ceremony of the Salt Lake City Winter Olympics, had said it was a team whose country is accused of sponsoring terrorism.    The first appearance of a U.S. wrestling team in Iran was in 1998 which was welcomed in the arena with wild applause by the Iranian crowd, surprising both the American athletes and Iranian officials.    Despite political hostilities over the last two decades, Teheran and Washington have been conducting sports diplomacy similar to that of the 1970s when a team of American table tennis players went to China as a prelude to improved ties between the two states.