On the heels of the bombshell revelation that Russia may have known in advance about the Syrian chemical weapons attack, the White House abruptly changed a background briefing on Russia to a non-reportable "off-the-record" briefing.

Earlier, we reported that a senior U.S. official says that Russia knew, in advance, of Bashar al-Assad’s chemical weapons attack on civilians, despite Donald Trump’s initial insistence that Russia was not involved.

Since then, the White House has taken a very unusual step that was described in this baffling pool report (via email from The White House):

From: Joseph, Cameron
Sent: Monday, April 10, 2017 6:06 PM
Subject: Pool report 5: Briefing made off-record

The White House had promised a background briefing on Russia. It was changed when it began to an off-the-record, un-reportable briefing. Michael Anton offered to answer any questions about what was discussed.

Cameron Joseph
Washington Bureau Chief
New York Daily News

Background briefings are fairly common, off-the-record briefings less so, and canceling one or the other happens occasionally. But, as someone who worked as a White House reporter for seven years, beginning a briefing on background and changing it to an off-the-record is something I have never heard of.

The unusual circumstances allowed the pool reporter a loophole to reveal at least one source for the briefing, mysterious Trump senior national security official Michael Anton. Ordinarily, officials at a background or off-the-record briefing are anonymous, but the reporter took advantage of the situation to get Anton’s name out.

Whatever the reason for the change, its occurrence, after yet another blow to Trump’s Syria airstrike mythology, hardly seems coincidental, but because the White House is forbidding journalists to report on it, we may never know.