The forces have been deployed at the request of the Philippine government, the embassy said.
The Philippine armed forces have been fighting the ISIS-linked Maute militants for control of the city of Marawi in the southern Mindanao region.
Dozens of Philippine troops and militants have been reported killed in fighting, including more than a dozen marines Friday.
The US Embassy said it couldn’t give specifics on the nature of the American support for “security reasons.”
US Special Operations Forces “have been providing support and assistance in response to Philippine government requests for many years,” the embassy said.
“As we have in the past, we routinely consult with our Filipino partners at senior levels to support the Duterte administration’s counterterrorism efforts,” the embassy said, referring to President Rodrigo Duterte.
A ‘temporary setback’
At least 13 Philippine marines were killed and 40 others wounded Friday during fighting with Maute militants in Marawi, the Philippine military said Saturday.
The fatalities occurred during a clearing operation over a 14-hour period.
The deaths bring the toll in the three-week Marawi campaign to 58 Philippine troops and at least 140 extremist militants, according to the state-run Philippine News Agency.
“This temporary setback has not diminished our resolve a bit,” said Marine Col. Edgard Arevalo, a military spokesman.
“It instead primed up our determination to continue our prudent advances to neutralize the enemy, save the innocent lives trapped in the fight, and set the conditions for the rehabilitation and reconstruction of Marawi.”
Fighting the militants’ message online
The fight against the Maute militants is proceeding on social media as well as the ground.
The Philippine military has called on Facebook to close 63 accounts linked to Maute militants engaged in the fighting.
At a press conference Friday in Marawi, Lt. Col. Jo-Ar Herrera said the military had uncovered accounts used by militants that focus on “spreading propaganda messaging and misinformation.”
Without confirming the request from the Philippines, a Facebook spokesman said the company has “well-established law enforcement channels for governments to contact us about emergencies.”
He said that Facebook removes any account tied to “groups or people that engage in terrorist activity, or posts that express support for terrorism.”
The request to Facebook comes just before the military’s goal of liberating Marawi by June 12 — the country’s Independence Day.
CNN’s Spencer Feingold contributed to this report.