TOKYO (AP) — Japanese Prime Minister Shinzo Abe sent a religious offering Monday to a Tokyo shrine that honors the dead, including executed war criminals — long a source of tension with Japan's neighbors China and South Korea.

Abe's offering at the Yasukuni Shrine marks the April 21-23 spring festival, one of the shrine's key annual events. But the move suggests he will not go to Yasukuni ahead of President Barack Obama's visit beginning Wednesday.

Chief Cabinet Secretary Yoshihide Suga said Abe's offerings were private and "would not in any way affect the summit talks (with Obama)."

Abe presented a pair of "masakaki," traditional Shinto-style decorations of tree branches and other ornaments, along with a wooden plate carrying his name and title.

Yasukui enshrines 2.5 million war dead including 14 Class A war criminals from World War II. The shrine has been a flashpoint between Japan and neighbors China and both Koreas. They see Yasukuni as a symbol of Japan's past militarism, and repeated visits by Japanese leaders as a lack of remorse over wartime history.

Abe's past remarks suggesting revisionist views about Japan's wartime history, and his push to step up Japan's national security and defense has prompted caution from the neighbors.

On Monday, about 270 people, including Japanese families and their South Korean counterparts, filed a lawsuit asking the Tokyo District Court to rule on the constitutionality of Abe's Yasukuni visit in December and suspend future visits. They argued Abe not only violated the separation of state and religion but worsened relations with Japan's neighbors, endangering the country's national security, and demanded 10,000 yen ($100) each in compensation.

Two cabinet ministers have prayed at Yasukuni recently — the national public safety chief on Sunday and the interior minister the previous week. Dozens of lawmakers are set to visit the shrine Tuesday.

Late last month, Obama helped to bring together Abe and South Korean President Park Geun-hye for their first face-to-face meeting since they took office more than a year ago. The absence of such a meeting between the leaders of key U.S. allies in Asia was a deep concern for Washington.

Conservative politicians who visit the shrine argue they are only making a pacifist pledge by praying for those who died in the war. Abe was mum Monday about his donations.

Abe regularly visited Yasukuni until he became prime minister, and has visited only once in December since taking office at the end of 2012. That visit has infuriated South Korea and China, worsening ties with already chilling ties with them over territorial and history issues. Washington said Abe's visit was disappointing.