The Liberal Democrat leader who has travelled regularly in the Balkans, spoke on a live satellite link from Skopje to the Ministry of Defence.
He said people had to understand that the Yugoslav President Slobodan Milosevic was using Kosovar refugees as an instrument of war to destabilise surrounding countries, and Mr Ashdown warned of the dangers of allowing him to succeed in that.
"Milosevic could win by destabilising Macedonia. We could lose there without even entering Kosovo," Mr Ashown said. "We have to win on that plane just as we have to deny him victory on every other."
He also repeated his view, now increasingly being echoed by the government, that the conflict would require ground troops even if Mr Milosevic refused to sign a peace deal. "It will come to ground troops in the end, whether President Milosevic agrees or not," said Mr Ashdown. But this should wait until Nato commanders judged the time was right.
"There's a moment when the risk will be acceptable for our troops to do what must be done if that's what it must come to. But that moment has not yet arrived, and anybody who thinks it has is going to be in danger of making sure we kill a lot of our young soldiers."
Mr Ashdown said every one refugee he had spoken to supported the air campaign, even some who were in the convoy accidentally bombed by Nato.
"They said the difference is that Nato is not trying to kill us. If it does, it does so by accident. Milosevic is trying to kill us."