BEIJING, April 23 -- The US-Japan alliance, a bilateral arrangement made in the Cold War, should not undermine China's territorial sovereignty and legitimate rights, a Chinese spokesman said on Wednesday.

The comment came after U.S. President Barack Obama said the Diaoyu Islands "fall within the scope of Article 5 of the US-Japan Treaty of Mutual Cooperation and Security" in an interview with the Yomiuri Shimbun newspaper ahead of his arrival in Tokyo on Wednesday.

"We firmly oppose putting the Diaoyu Islands within the scope of the US-Japan Treaty of Mutual Cooperation and Security," Foreign Ministry spokesman Qin Gang said at a daily news briefing.

Qin urged the United States to respect facts, take a responsible attitude, and honor its commitment of not taking sides on territorial sovereignty issues.

He also said the United States should be cautious with its words and deeds so as to play a constructive role in regional peace and stability.

He said China's stance on the Diaoyu Islands is consistent and clear, since these islands are an inherent part of Chinese territory and China holds indisputable sovereignty over them.

Japan's occupation of the islands are "illegal and invalid." Its provocations on the issue are "unjustified," the spokesman said.

"No one can shake our determination to safeguard national territorial sovereignty and maritime interests," Qin added.

Japan occupied the Diaoyu Islands during the Sino-Japanese War in 1895. After World War II, the islands were returned to China in accordance with such international legal documents as the Cairo Declaration and the Potsdam Proclamation.

In 1951, Japan, the United States and a number of other countries signed the Treaty of San Francisco, with China being excluded from it, and the treaty placed the Nansei Islands south of the 29th parallel of North Latitude under the United States' trusteeship. The Nansei Islands placed under the U.S. administration did not include Diaoyu Islands, however.

The United States arbitrarily expanded its jurisdiction to include the Diaoyu Islands later, despite the Chinese government's firm opposition.

In 1971, Japan and the United States signed the Okinawa Reversion Agreement, which provided that the Ryukyu Islands and the Diaoyu Islands would be "returned" to Japan. The move triggered strong opposition from the Chinese government and people.

As China and Japan were normalizing relations and concluding the Sino-Japanese Treaty of Peace and Friendship in the 1970s, the then leaders of the two countries, acting in the larger interest of China-Japan relations, reached consensus on "leaving the issue of Diaoyu Dao (Islands) to be resolved later."

In 2012, Tokyo moved unilaterally to "purchase" and "nationalize" the Diaoyu Islands, seriously straining China-Japan relations.