Washington, March 3 : China is investing aggressively to narrow Americaâ??s long-held undersea advantage, two senior US naval leaders told lawmakers.

They spoke at a hearing of the US-China Economic and Security Review Commission titled â??Part of Your World: US-China Competition Under the Sea.â??

Vice Admiral Richard Seif, Commander of US Naval Submarine Forces, said Americaâ??s edge beneath the waves remains strong but is under pressure.

â??Americaâ??s military advantage under the sea has been a decisive, enduring source of deterrence and warfighting leverage in the Indo-Pacific,â?? Seif said. He warned that â??advantages erode if they are not maintained.â??

Seif said China is working to narrow the US â??stealth margin.â?? He cited rapid submarine modernisation, stronger anti-submarine warfare capabilities, and seabed-sensing networks, sometimes described as an â??Underwater Great Wall.â??

He said Beijingâ??s investments aim to reduce US freedom of action in key maritime approaches, especially near chokepoints and within the first island chain.

Seif outlined four core advantages in the undersea domain: stealth and survivability, power projection, sea denial and sea control, and strategic deterrence.

â??Submarines remain the most survivable military platforms,â?? he said. Their ability to operate undetected, he added, underpins credible US response options in a crisis.

Seif cautioned that even incremental improvements in Chinese quieting, sensors, and weapons could shift the balance in contested waters.

To preserve the US edge, he urged prioritising submarine readiness, strengthening the industrial base, speeding maintenance, investing in unmanned systems, and deepening allied interoperability.

â??The best submarine is the one that is ready, crewed, and forward when needed,â?? he said.

Rear Admiral Mike Brookes, Commander of the Office of Naval Intelligence, echoed the warning.

He said Chinaâ??s undersea modernisation is part of a broader effort to contest US maritime superiority.

China operates â??one of the worldâ??s largest submarine fleets,â?? with more than 60 boats, including nuclear-powered attack submarines, ballistic missile submarines, and advanced diesel-electric platforms, Brookes testified.

He said Beijing is shifting toward a more nuclear-powered fleet and expanding production capacity to sustain growth into the 2030s.

Brookes described Chinaâ??s â??systems confrontationâ?? approach. It integrates submarines, aircraft, seabed sensors and unmanned platforms into a networked anti-submarine architecture.

The goal, he said, is to improve detection and tracking of US submarines in strategically vital waters and raise the cost of American intervention in a crisis.

Brookes also pointed to Chinaâ??s investment in unmanned undersea vehicles, seabed sensor networks and deep-sea mining technologies.

â??China is pursuing a unified approach linking strategy, naval modernization, seabed infrastructure, and resource extraction,â?? he said.

He warned that undersea cables and seabed systems could become targets in a conflict.

By 2040, Brookes said, the PLA Navyâ??s undersea forces â??may credibly challenge US regional maritime dominance,â?? complicating crisis response and allied defence in the Indo-Pacific.

Both officers stressed that the issue is not making the ocean fully transparent. It is about narrowing the US margin of stealth in key areas.

They said the stakes go beyond military balance. The undersea domain carries most global data traffic and financial transactions. That makes cable security and seabed resilience critical to economic stability.

For India and other Indo-Pacific nations, the testimony highlighted Chinaâ??s expanding submarine reach and growing presence in the Indian Ocean.

The message from the hearing was clear: the United States still holds a decisive undersea advantage, but keeping it will require sustained investment, innovation and close coordination with allies as rivalry moves deeper below the surface.

/IANS