Al-Jazeera Video: US analyst: Syria scud missiles 'a profound escalation'

"Human Rights Watch has reported that the Syrian government has been using incendiary scud missiles against the opposition in the north of the country.

The missiles contain highly flammable materials designed to cause severe burns.

Speaking to Al Jazeera from Washington, Mark Perry, military and foreign affairs analyst, says the reports are "credible", but the use of the unmanned missiles is a "very desperate measure" by the forces of Bashar al-Assad, the Syrian president.

Perry, author of "Talking to Terrorists: Why America Must Engage with its Enemies", tells Al Jazeera's Tony Harris that the use of the missiles may be a sign that the Assad forces "are up against a wall" and running out of pilots or helicopters with which to fire back at the armed opposition.

"If we want Assad overthrown, and we do, we're going to have to make the difficult choice of just saying 'let's do it'," he told Al Jazeera."