China demanded an investigation Wednesday after the U.S. military's admission the day before that it had accidentally shipped intercontinental ballistic missile parts to Taiwan.

"We have expressed deep concern and strong discontent on this incident and lodged representation with the U.S. side," China's state news media cited Foreign Ministry spokesman Qin Gang as saying.

The U.S. Pentagon revealed on Tuesday that it had mistakenly shipped four electrical fuses for nuclear missiles to Taiwan in 2006 instead of helicopter batteries. Taiwanese authorities alerted the U.S. to the mistake.

"We demand the U.S. side to conduct a thorough investigation into this incident … and eradicate the negative impact and evil consequences hence incurred," Qin told reporters.

President George W. Bush has told his Chinese counterpart, Hu Jin Tao, that the fuses were shipped to Taiwan "by mistake." Bush's national security advisor, Stephen Hadley, told journalists in Wasington that the issue came up during a telephone conversation on Wednesday between Bush and Hu.

 "Basically, the president indicated that a mistake had been made," Hadley said. U.S. officials have stressed that the shipment didn't contain nuclear material.

It's the second time in the past year that the U.S. military has admitted to a mistake involving nuclear missiles. Last September, a B-52 bomber flown from Louisiana to North Dakota was armed with six nuclear warheads, unbeknownst to the pilot and crew aboard, prompting an investigation and the firing of a commander.

The latest missile mistake is a particularly sensitive matter since China objects to the U.S. providing Taiwan with weapons.

Beijing claims the island as part of China and has threatened a military attack if Taiwan ever declares formal independence.

With files from the Associated Press