US President Donald Trump has approved $ 4.5 million in aid to the White Helmets, a civil defense organization in opposition factions in Syria, the White House said Tuesday.

White House spokeswoman Stephanie Gresham said in a statement that Trump's aid to the White Helmets was part of "continued US support for the important and valuable work of the organization in the country."

The White Helmets received international recognition for its work under heavy shelling to recover victims from rubble and take them to hospitals.

Russian-backed Syrian forces have repeatedly targeted White Helmets, saying they are not independent but support opposition fighters.

The financial aid comes amid a wave of sharp criticism of Trump in the United States and abroad for his decision to withdraw US troops from Kurdish areas in northern Syria near the border with Turkey.

His decision effectively gave Ankara a green light to launch a cross-border military operation against Kurdish guerrillas, whom Turkey sees as a security threat.