WASHINGTON — A Pentagon plan for the coming assault on Raqqa, the Islamic State capital in Syria, calls for significant U.S. 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 U.S. officials.

The military's favored option among several variations under White House review, the proposal would ease a number of restrictions on U.S. activities imposed during the Obama administration.

Officials involved in the planning have proposed lifting a cap on the size of the U.S. 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 militants in Syria, Iraq and beyond, received the plan Monday 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, U.S. 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 side by side with Russian and Syrian government forces with the same apparent objective.

Approval of the Raqqa plan would shut the door on Turkey's demands that Syrian Kurds, considered terrorists by Ankara, be denied U.S. equipment and kept out of the upcoming offensive.