BEIJING — The Chinese announced Saturday a series of harsh retaliatory measures in protest of the Pentagon’s $6 billion arms sale to Taiwan, including a suspension of security exchanges and threatened sanctions on U.S. companies selling to Taiwan.

“The U.S. decision seriously endangers China’s national security and harms China’s core interests,” the Defense Ministry said in a statement attributed to spokesman Huang Xueping.

Denunciations from Beijing over arms sales to Taiwan have an element of ritual about them, but the threat of sanctions on U.S. arms contractors is a new one. It remains to be seen whether China will follow through, given its need for commercial aircraft and aviation systems.

“Beijing doesn’t want to overreach,” said Bonnie Glaser, a senior fellow at the Center for Strategic and International Studies in Washington. “… In the aftermath of the Google incident, Beijing needs to think carefully before taking measures that would sour the business community on China.”

The biggest immediate casualty of the Taiwan arms sale may be President Barack Obama’s nuclear security summit planned for April. It had been hoped that Chinese President Hu Jintao would attend; now China is more likely to send a lower-ranking official. But in various statements Saturday, the Chinese government used the word “postpone” rather than cancel, hinting that normal dialogue will resume after several months.

On Saturday, the State Department defended the arms deal, saying, “such sales contribute to maintaining security and stability across the Taiwan Strait.” Under the 1979 Taiwan Relations Act, the U.S. is committed to supplying weapons to Taiwan to defend itself from a mainland attack. China considers Taiwan a breakaway province.

Strained relations

Tensions between China and the U.S. have flared in recent months over Google’s accusation that China was behind a series of computer attacks, and Secretary of State Hillary Clinton has stepped in to chide China about Internet censorship. The United States has also admonished Beijing over its reluctance to join in a fresh round of international sanctions against Iran for its nuclear program. And the Dalai Lama, Tibet’s spiritual leader, plans to visit the United States next month and is expected to seek a meeting with President Barack Obama — a move sure to infuriate Beijing.