Paul Moss

Intelligence sources estimate there are still between 5,000 and 7,000 members of the extremist Islamic State group at large in Iraq and Syria, some of them in sleeper cells which carry out regular attacks.

And there was a terrible reminder of that on Saturday, when three Americans were killed by a gunman at an army base close to Syria's famous ruins of Palmyra.

Donald Trump, speaking next to a rather noisy helicopter, reacted to the news.

It was an ambush, terrible.

We also have three wounded.

They seem to be doing pretty well.

But we mourn the loss.

The president, the new president of Syria is, as they told me, and I'm not surprised, he's devastated by what happened.

This was an ISIS attack on us and Syria.

It's pointed that Mr Trump took the trouble there to refer to the stance of Syria's president, Ahmad al-Sharah, a sign of how things have changed in the relations between Washington and Syria.

As our correspondent in Washington, Sean Dilley, explains.

Ahmad al-Sharah was once upon a time a sworn enemy of the United States.

The politics in Syria is, of course, very complex.

He was a rebel.

overthrowing Assad, the previous president in Syria.

So once upon a time, the two countries really would have had absolutely no love lost between them.

Last month, however, President Trump had welcomed the new Syrian president into the White House, into the fold.

He'd lifted sanctions on Syria, which had been crippling the country.

And the quid pro quo for that is the expectation that the US wants Syria to help out

lower that heat in the region with its neighboring countries in Israel.