Washington's top diplomat on Sunday, after talks with Israel's Benjamin Netanyahu, warned Syria that it was not off the hook following a US-Russian deal to destroy its chemical weapons stockpile.

On a whirlwind visit to Jerusalem for talks with Netanyahu on Syria and on peace talks with the Palestinians, US Secretary of State John Kerry made clear that the agreement with Moscow had not removed the option of a US-led military strike.

"The threat of force remains, the threat is real," Kerry said at a news conference after a four-hour meeting with the Israeli premier.