WASHINGTON • A Pentagon plan for the coming assault on Raqqa, the ISIS capital in Syria, calls for significant US military participation, including increased Special Operations forces, attack helicopters and artillery, and arms supplies to the main Syrian Kurdish and Arab fighting force on the ground, according to United States officials.
The proposal - the military's favoured option among several variations currently under White House review - would ease a number of restrictions on US activities imposed during former president Barack Obama's administration.
Officials involved in the planning have proposed lifting a cap on the size of the US military contingent in Syria, currently numbering about 500 Special Operations trainers and advisers to the combined Syrian Democratic Forces. While the Americans would not be directly involved in ground combat, the proposal would allow them to work closer to the front line and would delegate more decision-making authority down the military line from Washington.
President Donald Trump, who campaigned on a pledge to expand the fight against the militants in Syria, Iraq and beyond, received the plan after giving the Pentagon 30 days to prepare it.
But in a conflict where nothing has been as simple as anticipated, the Raqqa offensive has already sparked new alliances. In just the past two days, US forces intended for the Raqqa battle have had to detour to a town in northern Syria to head off a confrontation between two American allied forces - Turkish and Syrian Kurdish fighters. There, they have found themselves effectively side by side with Russian and Syrian government forces with the same apparent objective.
Approval of the Raqqa plan would effectively shut the door on Turkey's demands that Syrian Kurds, who are considered terrorists by Ankara, be denied equipment from the US and kept out of the upcoming offensive.
Turkish President Recep Tayyip Erdogan has said that arming and including the Kurdish People's Protection Units (YPG) in the operation is unacceptable and has vowed to move his own troops and Turkish-allied Syrian rebel forces towards Raqqa.
United States officials, some of whom spoke on the condition of anonymity about the still-secret planning, believe Mr Erdogan's tough talk is motivated primarily by domestic politics, specifically a desire to bolster prospects for an April 16 nationwide referendum that would transform Turkey's governing system to give more power to the presidency.
US talks with Turkey, a Nato ally and coalition member, are ongoing. But events over the past several days in and around the town of Manbij have injected a new element in the conflict that could either help the Americans avoid a direct clash with Ankara, or set the many forces now converging on the town on the path towards a new confrontation.
Manbij, located near the Turkish border about 135km north-west of Raqqa, was captured by the Islamic State in Iraq and Syria (ISIS) three years ago and retaken last August by the YPG, backed by US air strikes and advisers. The town now forms the western edge of a militant-cleared border strip extending to neighbouring Iraq.
The US had promised the Turks that Kurdish control would not extend to the west beyond the nearby Euphrates River.
On Saturday, the US military confirmed that it had "increased force presence in and around Manbij to deter hostile acts, enhance governance and ensure there's no persistent YPG presence", effectively inserting US forces to keep two coalition members - Turkey and the Syrian Kurds - from fighting.
In postings on his Twitter account, coalition spokesman Colonel John Dorrian said the coalition "has taken this deliberate action to reassure coalition (members) and partner forces, deter aggression and keep focus on defeating ISIS".
The US and Russia have managed to avoid confrontation in Syria's separate civil war, where they are on opposing sides. Mr Trump has said repeatedly that the two powers should cooperate against ISIS.