ChatGPT developer OpenAI is restricting access to its latest artificial intelligence (AI) model at the request of the US government, the company said on Friday.

In a blog post, OpenAI said it had launched a "limited preview" of its GPT-5.6 series, Sol, Terra and Luna.

"As part of our ongoing engagement with the US government, we previewed our plans and the models’ capabilities ahead of today’s launch," the post said.

"At their request, we are starting with a limited preview for a small group of trusted partners whose participation has been shared with the government, before releasing more broadly."

The company said it plans to make the models generally available in the coming weeks.