The US will send 250 additional military personnel to Syria to support local militias in the fight against ISIS, officials have said.
The goal, they say, is to encourage more Sunni Arabs to join Kurdish fighters in north-eastern Syria.
The new deployment will bring to 300 the number of US forces in non-combat roles in Syria.
Most of the additional personnel will be special operation forces, the AP reports. The group will also include medical and logistical troops, it adds.
A formal announcement is expected from President Barack Obama during his visit to Hannover on April 25, where he will discuss Syria and other foreign policy issues with leaders of the UK, Germany, France and Italy.
Of those, four million have fled abroad, including growing numbers who are making the dangerous journey to Europe.
The crisis has put pressure on leaders there, who are struggling to halt a massive influx of migrants and refugees.
Speaking alongside Barack Obama, German Chancellor Angela Merkel on April 24 urged warring parties to set up safe zones in Syria where refugees would be protected within the country.
Angela Merkel expressed hope that such a plan might eventually be agreed at peace talks taking place in Geneva.
Barack Obama, however, said it would be “very difficult” for those zones to work without a large military commitment.
ISIS has lost parts of the territory it once controlled in Syria. Most recently, they were pushed back by Russian-backed Syrian forces from the strategic city of Palmyra.
The group has also had significant setbacks in Iraq, including the loss of Ramadi, the capital of Anbar province.
The US has led a coalition against the militant group in both Syria and Iraq.