YOKOHAMA -- Japan and the United States held a ceremony here Saturday to commemorate the 150th anniversary of the signing of the first treaty between the two nations.

Prime Minister Junichiro Koizumi described the two nations today as "partners cooperating in the global context."

"The cooperative relationship between our countries is profound and strong, as seen in the important role played by Japan and the United States toward the reconstruction of Afghanistan and Iraq," Koizumi said during the ceremony at a park near Yokohama port, where representatives of the two nations signed the Treaty of Peace and Amity in 1854.

The treaty paved the way for Japan to open up to foreign influences after more than two centuries of self-imposed isolation under the Tokugawa shogunate.

U.S. President George W. Bush joined the ceremony via a video message, in which he said that America has no closer ally than Japan today. "Our governments work together to stop the proliferation of weapons of mass destruction, to bring peace to strife-torn lands, and to defeat the terrorists that threaten our common values," he said.

The ceremony was also attended by U.S. Ambassador Howard Baker, Environment Minister Yuriko Koike, Yokohama Mayor Hiroshi Nakada and Yoshio Okawara, former ambassador to the U.S.