President Joe Biden has vowed to respond to the attack which left three US troops dead in Jordan, as well as 25 injured in an unmanned drone strike. Mr Biden said the strike on a military outpost in Jordan, near the Syrian border had been carried out by an Iranian-backed militia. "One last thing, I want to point out we had a tough day. Last night when we lost three brave soldiers in an attack on one of our bases. And I ask for a moment of silence. And we shall respond."The Democratic president made the remarks at a campaign event in South Carolina and asked attendees to join him for a moment of silence.Reuters