The committee’s Republican chairwoman, Ileana Ros-Lehtinen, dubbed China a “schoolyard bully towards its maritime neighbours” that aspired to be the dominant power in Asia, controlling vital sea lanes that could be used to choke off commerce and oil shipments. She said the US would stand by its allies, the Philippines and Japan.

“Other global crises must not distract from our vital national interests in the South China Sea and the western Pacific,” she told a hearing addressing the issue.

Top Democrat Howard Berman said the Obama administration has repeatedly made clear to Beijing that the US will not allow China to assert hegemony over the region. He said the US must continue to press China to resolve its claims peacefully.

China and five of its neighbours, including the Philippines and Vietnam, have overlapping claims to several small, but potentially energy-rich areas of the South China Sea, that have become an increasing focus of bickering and confrontation. In July, China upped the ante when it created a city and military garrison on a remote island to strengthen its control over disputed islands.

The United States criticised that as undermining efforts to manage and resolve disputes through diplomacy. That angered China, which says it has no aggressive intent.

The US, which remains the world’s predominant military power, says it does not take a position on the competing territorial claims, but has a national security interest in the maintenance of peace and stability in the region. On Tuesday it urged “cooler heads to prevail” in a separate island dispute between Japan and China in the East China Sea.

Republican lawmaker Mike Kelly questioned the ability of an indebted US to sustain its military presence across the world, and suggested China was now “the toughest guy in the neighbourhood” that would call the shots on policy there.

“At some point we better wake up and smell the coffee,” Kelly said. “We have a diminished influence because we really don’t have the ability at times to do what we say we are going to do.”

Democratic lawmaker Brad Sherman said US allies needed to bear more of the security burden, as during the Cold War against the Soviet Union.

“Those nations in the Asia-Pacific region, particularly those that have concerns with China’s expansionary claims ought to be devoting a reasonable portion of GDP to their own naval defence,” he said.

On Thursday, the House Intelligence Committee will question executives of two major Chinese technology companies as it probes allegations that the firms’ involvement in the US market could pose a national security risk.

Also Wednesday, another House panel examined allegations of human organs of religious and political dissidents being harvested by Chinese authorities.

Staunch China critic, Republican lawmaker Chris Smith, alleged that kidneys, livers, lungs, hearts and corneas were taken from recently deceased prisoners and that China’s military doctors may also be harvesting organs from live prisoners. He conceded that much of the evidence is circumstantial, but decried the harvesting as a “barbaric practice that must be stopped.”

In an annual human rights review this year, the US State Department cited reports of organ harvesting in China, particularly from practitioners of the banned religious sect, Falun Gong, and the Uighur ethnic minority.

China reportedly plans to abolish organ harvesting of death-row inmates within the next five years.