President Rodrigo Duterte said on Tuesday wanted Japan for his first official visit to a country outside the Association of Southeast Asian Nations (ASEAN) but Tokyo gave a definite date.

In a speech during the mass oath taking of newly-appointed government officials in Malacanang, Duterte said: "I was supposed to go to Japan ahead. But Japan gave a definite date...so I cannot do anything about it."

Duterte’s official visit to Japan since he became president in June is on October 25-27. He will make a state call on Emperor Akihito and Prime Minister Shinzo Abe will host a dinner for him, the Japanese foreign ministry said in a statement.

He said China repeatedly invited him, so he accepted and he would go there first because the date was available. He will visit Beijing on October 18-21 after his trip to Brunei.

"I will go to Brunei, then directly go to China, then part of that is Japan," he said.

Earlier reports came out that Tokyo was disappointed that he would first visit China than Japan.

Contrary to reports that other countries have bigger assistance to the Philippines, he said, "it's the Japanese government, which has the biggest aid."

Latest data from the National Economic and Development Authority (NEDA) showed that in the second quarter of 2015, Japan is the biggest source of official development assistance loan of the Philippines valued at $3.13 billion among foreign governments.

Japan is second to World Bank, with $3.44 billion, as the top source of ODA loans during the same period.

After Japan, Duterte said he might go to Russia.

“The Government of Japan sincerely welcomes the visit of the President and hopes the visit will further strengthen the friendly relations between Japan and the Republic of Philippines,” it added.

Japan and the United States have supported the Philippines’ move to seek international arbitration against China over its claim in the South China Sea that overlaps with Manila.

China has opposed the arbitration and prefers one-on-one negotiations with rival claimant countries. Relations between the Philippines and China deteriorated when the Philippines brought it to international arbitration over the territorial issues in January 2013. Celerina Monte/DMS