The C-17 Globemasters landed in Chengdu, the provincial capital of Sichuan, and the aid supplies were offloaded onto trucks for shipment into the epicenter.
It was the first assistance from a foreign military to arrive in China since the May 12 quake, the official Xinhua News agency said.
"The current suffering of the people of China as a result of this terrible tragedy is in the thoughts and prayers of the American people," Brig. Gen. Charles Hooper, defense attache at the U.S. Embassy in Beijing who accompanied the shipment, told AP Television News.
The Air Force said it delivered nearly 200,000 pounds of relief supplies to China aboard the C-17s. The aircraft are assigned to the 15th Airlift Wing, Hickam Air Force Base, Hawaii, and the 3rd Wing, Elmendorf Air Force Base, Alaska.
Most of the aid was to be sent to Beichuan, a mountain area in the northern part of the province that was among the hardest-hit areas in the magnitude 7.9 quake, said Sr. Capt. Guan Youfei of the Chinese Defense Ministry's foreign affairs office.
"We are going to deliver this aid to the local governments as soon as possible," he said.
China also has allowed foreign earthquake rescue experts to the disaster area, after reversing its initial reluctance to accepting their help.
The earthquake relief mission marks the second time this year the U.S. has provided humanitarian assistance to China. In February, a U.S. Pacific Command mission sent a C-17 from Hickam to deliver winter relief supplies when 19 Chinese provinces experienced the most severe winter storms in 50 years.
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