Five past and present world leaders are urging U.S. President Barack Obama to join them at a gathering of Nobel Peace Prize laureates in Hiroshima.

No sitting American president has ever visited the Japanese city, where the United States dropped the first atomic bomb in 1945.

The appeal to President Obama comes in a letter from former Soviet President Mikhail Gorbachev, Lech Walesa of Poland, Frederik de Klerk of South Africa and Oscar Arias Sanchez of Costa Rica.  Jose Ramos-Horta, the current president of East Timor, also signed.

Mr. Obama has not announced any plans to attend the November meeting, which is an annual event.  He is scheduled to be in Japan on Nov. 13 and 14, though, for a summit of Asia-Pacific leaders.

The peace laureates write in the letter that they are encouraged by Mr. Obama's stated desire to rid the world of nuclear weapons.

The United States sent a representative to an annual ceremony marking the anniversary of the Hiroshima bombing for the first time this year.

Some information for this report was provided by AP and AFP.