 The United States accused China on Tuesday of adopting a more aggressive military stance in the South China Sea as a naval confrontation caused anger in Beijing and raised tension before a US visit by China's foreign minister. The incident involving five Chinese ships and a US Navy survey vessel threatened to further complicate ties between the two powers as they wrestle with a joint response to the global economic crisis and prepare for a G20 summit in London next month. National Intelligence Director Dennis Blair told the US Congress the Chinese have become more assertive in staking claims to international waters around economic zones and were "more military, aggressive, forward-looking than we saw a couple years before" in Southeast Asia and the South China Sea. Blair said it was unclear whether Beijing would use its growing military power "for good or pushing people around." The United States accused China of harassing the US ship, the USNS Impeccable, in international waters off China's Hainan island, site of a major submarine base and other naval installations. The US Embassy in Beijing filed a protest with China. China countered that the United States had distorted the truth and violated international and Chinese laws. "The US claims are gravely in contravention of the facts and confuse black and white and they are totally unacceptable to China," Chinese Foreign Ministry spokesman Ma Zhaoxu said in Beijing. The exchange came as Chinese Foreign Minister Yang Jiechi arrived in Washington to lay the groundwork for a meeting between Chinese President Hu Jintao and U.S. President Barack Obama at the G20 summit. Yang has meetings planned on Wednesday with Secretary of State Hillary Clinton, who visited China last month, and Treasury Secretary Tim Geithner as the two countries seek a cooperative path on the global economic crisis and climate change. Analysts played down the long-term significance of the incident given the heavy agenda facing the two countries, but it added one more item of contention to an already difficult relationship. TIBETAN ANNIVERSARY The charges over the naval confrontation also coincided with US demonstrations to mark the 50th anniversary of the Chinese occupation of Tibet and the Dalai Lama's exile. Clinton was accused by rights groups of soft-pedaling human rights concerns during her visit to China last month. State Department spokesman Robert Wood said he would be "surprised" if the issue of Tibet was not raised during Yang's meeting with Clinton. He said the United States wants to see a substantive dialogue between the Chinese government and representatives of the Dalai Lama. "We're going to continue to raise this issue with the Chinese and do what we can to improve the situation on the ground," he said. Wood also issued a statement saying the United States was deeply concerned by the the human rights situation in Tibet. "We urge China to reconsider its policies in Tibet that have created tensions due to their harmful impact on Tibetan religion, culture, and livelihoods," the statement said. Blair called the incident in the South China Sea the most serious since a Chinese military plane collided with a US electronic surveillance plane off Hainan in April 2001, early in President George W Bush's administration. A Chinese pilot was killed, and the US plane made an emergency landing on the island. The American crew was released 10 days later, and the plane was returned. The United States said the Chinese actions appeared deliberate, and some analysts said China might be sending a message early in the Obama administration about its right to keep foreign navies from operating in its economic zones. A senior US defense official said the United States would continue to operate in international waters, but he stopped short of saying any US ocean surveillance vessels would return to the area where Sunday's incident occurred. The director of the Defense Intelligence Agency, Lieutenant General Michael Maples, told Congress that China was strengthening its ability to conduct military operations along its periphery and acquiring sophisticated air defenses from Russia. "It is building and fielding sophisticated weapon systems and testing new doctrines that it believes will allow it to prevail in regional conflicts and also counter traditional US military advantages," he said.