National Security Advisor John Bolton speaks to reporters as he announces that the U.S. will pull out of a treaty with Iran during a news conference in the White House briefing room in Washington, October 3, 2018.

The U.S.'s planned drawdown of troops in Syria will be conditioned upon an agreement with Turkey that protects Kurdish fighters in the region who have been pivotal to battling ISIS, White House national security advisor John Bolton said on Sunday.

Speaking to reporters in Jerusalem during a visit to Israel and Turkey, intended in part to reassure allies amid criticism over the White House's Syria decision, Bolton fielded numerous questions about Washington's support for its Kurdish partners, and the U.S.'s plans to reduce its footprint in the strife-torn country. He described the stipulation as President Donald Trump's official position.

The Kurds have been steadfast local allies in the fight to repel Islamic State (IS) in Syria. Trump's surprise decision last month to pull 2,000 U.S. troops from the country unsettled America's partners, leaving the Kurds especially vulnerable to Turkish attack or a takeover by the regime of Syrian President Bashar al Assad.

"We don't think the Turks ought to undertake military action that's not fully coordinated with and agreed to by the United States at a minimum, so they don't endanger our troops," Bolton said on Sunday. In addition, Turkey must "meet the president's requirement that the Syrian opposition forces that have fought with us are not endangered."

Bolton added that Trump is fully committed to the fight against terror, and as such "wants the ISIS caliphate destroyed." On Monday, the White House's top national security official is expected to travel to Turkey for talks with Turkish officials about their aims and capabilities in combating IS.