Two grey shapes, visible from satellites for most of this year at Cambodia’s Ream naval base, seem to confirm growing fears in Washington: that China is expanding its military footprint, beyond the three disputed islands in the South China Sea which it has already seized and fortified.

The shapes are type 056A corvettes of the Chinese navy - 1,500-tonne warships - and they have been berthed alongside a new, Chinese-built pier that is big enough to accommodate much larger vessels. Onshore there are other facilities, also built by China, which are presumed to be for the use of the Chinese navy.

The Cambodian government has repeatedly denied such a possibility, citing its constitution which bans any permanent foreign military presence, and stating that Ream is open to use by all friendly navies. Cambodia claims the ships are for training, and to prepare for this year’s Golden Dragon exercises. It also says China is constructing two new 056A corvettes for its own navy, and insists that the Chinese presence in Ream is not permanent, so does not count as a base.

That has not stopped US officials from expressing their concern over the expansion of the site, though, which satellite photographs show has, in addition to the new pier, a new dry dock, warehouses, and what look like administrative offices and living quarters with four basketball courts.