The White House has sent its national security adviser, John Bolton, on a mission to allay Israel's concerns about Donald Trump's decision to withdraw US troops from Syria.
The pull-out - which was widely criticised when it was first announced before Christmas - was initially expected to be completed within weeks, but the timetable has slowed as the US president acceded to requests from aides, allies and members of Congress for a more orderly exit.
Bolton planned to meet with Israel's prime minister Benjamin Netanyahu and other officials this weekend before travelling on to Turkey in a bout of shuttle diplomacy.
Israeli officials have expressed alarm that a swift withdrawal of the roughly 2,000 troops could enable Iran to expand its influence and presence in Syria, racked by a years-long civil war and the Isil militancy.
Trump's move has raised fears about clearing the way for a Turkish assault on Kurdish fighters in Syria who have fought alongside American troops against Isil extremists.
Turkey considers the Kurdish People's Protection Units, or YPG, a terrorist group linked to an insurgency within its own borders.
A Trump administration official told reporters Bolton intended to discuss the pace of the drawdown, as well as American troop levels in the region. Bolton was expected to explain that some US troops based in Syria to fight Isil will shift to Iraq with the same mission and that some US forces may remain at a military outpost in al-Tanf, southern Syria, to counter Iranian activity in the region.
Bolton is also expected to say the US will be "very supportive" of Israeli strikes on Iranian targets in Syria.
Bolton warned Syria's president, Bashar al-Assad, not to use the US drawdown as a pretext to use chemical weapons against Syrians, saying there is "no change" to the US position that their use is a "red line". America has, both under Barack Obama and Trump, carried out air-strikes in Syria in response to apparent chemical attacks, with the intention of deterring Assad.
Trump's announcement about the intended troop withdrawal was greeted by surprise and condemnation from many US and allies, and prompted the resignation of Defence Secretary Jim Mattis and the US special envoy for the anti-Isil coalition in protest.
Secretary of State Mike Pompeo is following Bolton to the Middle-East this week for an eight-country tour of Arab allies to shore up support for the administration's partners in the region.
While in Israel, Bolton planned to encourage officials to take a tougher stance against Chinese electronics manufacturers ZTE and Huawei after the US expressed concerns about potential cyber-penetration by those firms.
Bolton then goes to Turkey where he is expected to warn against an offensive targeting the Kurdish fighters in Syria.
© Associated Press