“We actually don’t know.” That’s how United States National Security Council spokesman John Kirby responded late last week in answer to a question about what information Washington possesses about the likelihood that China is about to get involved in the Ukraine war by sending weapons to Russia.

For a US administration that spent quite some time warning about the supposedly grave dangers of Chinese supplies of weapons to Russia, the admission that Washington actually knows very little on this score seems odd; if you know little, you are well advised to keep quiet.