"There is absolutely no change in the US position against the use of chemical weapons by the Syrian regime and absolutely no change in our position that any use of chemical weapons would be met by a very strong response, as we've done twice before," Bolton told reporters on his plane shortly before landing in Tel Aviv, Israel.
"So the regime, the Assad regime should be under no illusions on that question."
Bolton added: "As we elaborate how the withdrawal is going to occur and the circumstances, we don't want the Assad regime to see what we do as representing any diminution in our opposition to the use of weapons of mass destruction."