WASHINGTON — The United States on Tuesday added Syria to a blacklist of countries failing to abide by conventions barring human trafficking and slavery, a move which leads to sanctions and cuts in US aid.

"The government of Syria does not fully comply with the minimum standards for the elimination of trafficking and is not making significant efforts to do so," the 2012 Trafficking in Persons report said.

It voiced particular concerns about Filipina maids being sent to Syria via Dubai who were vulnerable to "conditions of forced labor" and to allegations reported by the United Nations that the Syrian opposition was using child soldiers.

US officials had not been able to fully assess the situation on the ground due to fierce fighting in the 15-month conflict, as the opposition seeks to oust President Bashar al-Assad, the report said.

But some 95 Filipina domestic workers were believed to have been trapped in the cities of Homs and Hama which have come under attack from the regime forces, and the government made no effort to help their embassy free them.

"Anecdotal evidence suggests that some economically desperate Syrian children are subjected to conditions of forced labor within the country, particularly by organized street begging rings," the report added.

While some Syrian women and girls were being forced into prostitution in neighboring Lebanon, it said.

Syria's designation on tier 3, the bottom of the ranking system, means the US administration could withhold non-humanitarian aid from October 1 and Syria could face US opposition to aid from bodies such as the World Bank and the International Monetary Fund.