The first Chinese surveillance balloon that the Pentagon found flying over sensitive US ballistic missile sites may be guided by advanced artificial intelligence technology, a US expert said Friday.

A second Chinese surveillance balloon was later spotted over Latin America, the Pentagon said, without specifying its exact location.

William Kim, a specialist in surveillance balloons at the Marathon Initiative think tank in Washington, told AFP that balloons are a valuable means of observation that are difficult to shoot down.

Kim said the first Chinese balloon looked like a normal weather balloon but with distinct characteristics.

Kim said the first Chinese balloon looked like a normal weather balloon but with distinct characteristics.

It has a quite large, visible "payload", the electronics for guidance and collecting information, powered by large solar panels.

It has a quite large, visible "payload", the electronics for guidance and collecting information, powered by large solar panels.

And it appears to have advanced steering technologies that the US military hasn't yet put in the air.

And it appears to have advanced steering technologies that the US military hasn't yet put in the air.

Artificial intelligence has made it possible for a balloon, just by reading the changes in the air around it, to adjust its altitude to guide it where it wants to go, Kim said.

"Before you either had to have a tether... or you just send it up and it just goes wherever the wind takes it," he said.

"Before you either had to have a tether... or you just send it up and it just goes wherever the wind takes it," he said.