Japanese Prime Minister Shinzo Abe vowed Friday that he would not "tolerate" any challenge to control over contested islands, after China's growing incursions into the area.
"We simply cannot tolerate any challenge now and in the future. No nation should make any miscalculation or underestimate the firmness of our resolve," Abe said at the Center for Strategic and International Studies in Washington.
"No one should ever doubt the robustness of the Japan-US alliance."
Speaking after talks at the White House with President Barack Obama, Abe also cautioned that "I have absolutely no intention to climb up the escalation ladder."
He called for the two nations to work on common interests and called Japan's relations with China "among the most important" with any country.
"The doors are always open on my side for the Chinese leaders," Abe said.
The Japanese leader insisted that history and international law proved that the islands -- known as the Senkaku in Japanese and the Diaoyu in Chinese -- "are Japan's sovereign territory."
Abe said that no one contested Japan's sovereignty between 1895, when Tokyo annexed the islands, and 1971, the year before the United States returned the islands along with Okinawa to Japan after seizing them in World War II.
Japan has often charged that China only became interested in the East China Sea territory in recent times after learning that it was potentially rich in oil and gas.
China disputes the Japanese position and argues that it has controlled the islands since the 1368-1644 Ming Dynasty. Taiwan also claims the area.