WASHINGTON ? The United States on Friday unveiled a $6.4 billion arms package for Taiwan to help counter China's rapidly growing military, risking the wrath of the rising Asian giant.

The arms package includes Patriot missiles, Black Hawk helicopters, and communications equipment for Taiwan's F-16 fleet. But it did not include new fighter aircraft themselves, which had been part of Taipei's wish list.

China considers Taiwan, where nationalists fled in 1949 after losing the mainland's civil war, to be a territory awaiting reunification, by force if necessary. It had warned Washington repeatedly against the arms sales.

The move is sure to complicate already difficult relations between Washington and Beijing amid discord over trade, human rights, Internet censorship and climate change policy.

The United States since 1979 has recognized Beijing as China's sole government. But Congress at the same time required the United States to sell Taiwan weapons for its self-defense.

"This is a clear demonstration of the commitment that this administration has to provide Taiwan the defensive weapons it needs," State Department spokesman Philip Crowley said.

"We think that this action is consistent with the US one-China policy... and contributes to maintaining security and stability across the Taiwan Strait," he said.

The sale marks the most potentially divisive act toward China by President Barack Obama, whose first year was devoted to broadening ties with Beijing despite criticism at home for not pushing harder on issues such as human rights and Tibet.

US officials said they called in a diplomat from the Chinese embassy on Friday morning to explain the Taiwan arms package.

Obama's national security advisor, former general James Jones, said moments before the announcement that the United States was being "transparent" with China.

"We all recognize that there are certain things that countries will do periodically that may not make everybody completely happy," he said at the Center for Strategic and International Relations, a Washington think-tank.

"But we are bent towards a new relationship with China as a rising power in the world, with influence on a variety of issues that go beyond the arms sales," he said, calling China a "very, very high priority" for the Obama administration.

The last US arms package for Taiwan, which was announced under previous president George W. Bush in October 2008, led China to snap off military relations with the United States for more than a year.

Analysts said China this time could retaliate by refusing to support sanctions on Iran, a key US priority. Secretary of State Hillary Clinton appealed to Beijing on Iran's nuclear program in remarks in Paris hours before the Taiwan sale was announced.

A senior US official, speaking on condition of anonymity, said that while the United States expected a strong reaction from China, it was hopeful that Obama's early diplomacy would prevent a serious deterioration in relations.

"We have a very mature relationship. We think we can get through issues like this," the official said.

The official added that the sale met an "urgent requirement" for Taiwan but also gave the leadership "greater confidence and ability to interact across the straits in a peaceful dialogue" with Beijing.

Taiwan's President Ma Ying-jeou has worked to improve relations with Beijing. His election in 2008 ended two decades of leadership in Taiwan that took a more confrontational approach with China.

But Ma has nonetheless appealed to the United States for weapons including the F-16 fighter-jets in light of China's military budget, which is shooting up by double digit percentages each year.

Officials denied they balked at the sale of F-16s to temper China's reaction, with Crowley saying the United States made its decision "based on our evaluation of the defensive needs of Taiwan."

The senior official who requested anonymity said that the Taiwan sale would also send a powerful signal to other Asian nations "that the US stands by its commitments."

"Others that depend on the United States for the maintenance of peace and stability can be reassured that our support is unwavering," he said.

The United States stations troops in South Korea and Japan, whose new government has butted heads with Washington over a controversial air force base.