Prime Minister Shinzo Abe's failure to include a pledge to observe the country's three nonnuclear principles in the annual memorial speech on Thursday remembering the victims of the Hiroshima atomic bomb attack is causing speculation the exclusion may be political.

In 2014 and 2013, Abe himself reconfirmed the pledge repeated by past prime ministers to "firmly maintain" the principles — of not possessing, producing or permitting nuclear weapons on Japanese territory — in the annual speech in the city that was devastated by an atomic bomb dropped by a U.S. plane on Aug. 6, 1945.

After the speech on Thursday, senior government officials downplayed the exclusion, pointing out the prime minister in the same speech emphasized his determination to make every effort to abolish nuclear weapons around the world. "(Maintaining) the three nonnuclear principles is a matter of course. It's unshaken," said Chief Cabinet Secretary Yoshihide Suga during a daily news conference.