President Barack Obama said Tuesday he expected governments in the Muslim world to protect American diplomats, despite their revulsion at a film made on US soil deemed offensive to their faith.

Obama said during a taping of the "Late Show with David Letterman" on CBS that securing US missions overseas was a top priority, following the killings of four Americans, including the US ambassador to Libya, in Benghazi last week.

"The message we have to send to the Muslim world is that we expect you to work with us, to keep our people safe," Obama said.

The president added that "as offensive as this video was -- and obviously we denounced it, the United States government had nothing to do with it -- that's never an excuse for violence."

Excerpts of the film "Innocence of Muslims," produced by a small group of US-based extremist Christians, appeared on YouTube and sparked a contagion of violence against American installations in the Arab world.