These may be the world's best warships. And they're not American

It's a growing problem that has United States naval commanders scratching their heads: How to keep up with China's ever-expanding fleet of warships.

Not only is China's navy already the world's largest, its numerical lead over the US is getting wider, with the head of the US Navy warning recently that American shipyards simply can't keep up. Some experts estimate China can build three warships in the time it takes the US to build one.

It is just one of the concerns, alongside Beijing's increasing aggression in the South China Sea and around Taiwan, that's likely to be weighing on the mind of US Defense Secretary Lloyd Austin as he joins top military figures from across the region at this weekend's Shangri-La Dialogue in Singapore.

The chance of a breakthrough on any of those issues this weekend appears slim, not least because China has pointedly rejected a US proposal for Austin to meet his Chinese counterpart Li Shangfu at the forum.

But experts who spoke to CNN before the summit say a potential solution to one of them - the Chinese fleet's numerical advantage - is within reach, if the US is prepared to think outside the box.

Washington, they say, has something Beijing doesn't: Allies in South Korea and Japan who are building some of the highest spec - and affordable - naval hardware on the oceans.

Buying ships from these countries, or even building US-designed vessels in their shipyards, could be a cost-effective way of closing the gap with China, they say.