American intelligence sources say Pakistan allowed China access to the downed US helicopter that was left behind in the raid that killed Osama bin Laden.
The Black Hawk helicopter was blown up by US Navy Seals after it crashed, but the tail remained largely intact.
The Financial Times newspaper says Chinese military engineers were allowed to take photographs and samples of the tail of the Black Hawk helicopter, which had a special skin and shape to deflect radar detection.
China is a major investor in telecommunications, ports and infrastructure in Pakistan.
bin Laden was killed at his compound in in Abbottabad, 1km from an army base on 2 May.
After the raid, US officials asked Pakistan not to let anyone view the remains of the helicopter.
It was brought back to the United States two weeks later following a trip by US Senator John Kerry.
Both Pakistan and Chinese officials have denied the latest reports.
