BEIRUT, Lebanon — Syrian officials warned Monday that they would deploy chemical weapons against any foreign intervention, a threat that appeared intended to ward off an attack by Western nations while also offering what officials in Washington called the most “direct confirmation” ever that Syria possesses a stockpile of unconventional armaments.

The warning came out of Damascus, veiled behind an assurance that the Syrian leadership would never use such weapons against its own citizens, describing chemical arms as outside the bounds of the kind of guerrilla warfare being fought internally.

“Any stock of W.M.D. or unconventional weapons that the Syrian Army possesses will never, never be used against the Syrian people or civilians during this crisis, under any circumstances,” a Foreign Ministry spokesman, Jihad Makdissi, said at a news conference shown live on Syrian state television, using the initials for weapons of mass destruction. “These weapons are made to be used strictly and only in the event of external aggression against the Syrian Arab Republic.”

Mr. Makdissi said that any such weapons were carefully monitored by the Syrian Army, and that ultimately their use would be decided by generals.