Updated

The State Department on Saturday backed U.S. plans to sell Taiwan $6.4 billion worth of arms in the face of China's threat to punish U.S. arms makers.

"Such sales contribute to maintaining security and stability across the Taiwan Strait," Laura Tischler, a State Department spokeswoman, told Reuters.

China suspended military exchange visits with the United States on Saturday in protest over the planned sales and warned the U.S. ambassador that the sales would harm already strained ties.

The state-run Xinhua News Agency cited the Defense Ministry as saying the suspension is due to the "bad impact" of the arms sales on the two countries' military relations.

China took a similar step in 2008 after the former Bush administration announced a multibillion-dollar arms sale to Taiwan. The latest arms sales could complicate the cooperation the U.S. seeks on issues ranging from Iran's nuclear program to the loosening of Internet controls, including a Google-China standoff over censorship.

Details of arms sale were posted Friday on a Pentagon Web site. It would include 60 UH-60M Black Hawk helicopters, 114 Patriot Advanced Capability-3 missiles, mine-hunting ships and information technology. U.S. lawmakers have 30 days to comment on the proposed sale. Without objections, it would proceed.

Taiwan is the most sensitive issue in U.S.-China relations. China claims the self-governing island as its own, while the United States is Taiwan's most important ally and largest arms supplier.

Though Taiwan's ties with China have warmed considerably since Taiwanese President Ma Ying-jeou took office 20 months ago, Beijing has threatened to invade if the island ever formalizes its de facto independence.

Both the U.S. and China have previously said they want to improve military ties, which have been frosty.

Earlier Saturday, Vice Foreign Minister He Yafei warned U.S. Ambassador Jon Huntsman that the sale would "cause consequences that both sides are unwilling to see." The vice minister urged that the sale be immediately canceled, it said.

The U.S. is "obstinately making the wrong decision," China's Foreign Ministry said in a statement.

A spokeswoman for the U.S. Embassy, Susan Stevenson, confirmed that China expressed its views, and said the embassy had no comment on the suspension of military visits.

Jin Canrong, a professor of international studies at China's Renmin University, said the sale would give Beijing a "fair and proper reason" to accelerate weapons testing.

Beijing has test-fired rockets in recent weeks for an anti-missile defense system in what security experts said was a display of anger at the pending arms sale.

Upcoming high-level visits that could be affected by the China's suspension of military exchanges. Gen. Chen Bingde, the Chinese military's chief of the general staff, was due to visit the U.S., while U.S. Secretary of Defense Robert Gates and Admiral Michael Mullen, Chairman of the U.S. Joint Chiefs of Staff, had planned to come to China.