Syrian opposition commanders told McClatchy on Tuesday that the U.S. has stopped paying and delivering arms to many so-called moderate pro-western rebels who are fighting to overthrow the country's regime.

"In November we received all kinds of support including salaries. This month support stopped completely," said Col. Fares Bayyoush, leader of the Fursan al Haqq Brigade in Kafr Nabel, a town about 20 miles south of the city of Idlib.

The CIA reportedly began covertly supplying Syrian rebel groups with weapons and funding back in 2012, but according to new reports from commanders, the CIA told them funding and arms are largely being withheld due to fighters' failure to stop the ever-advancing al-Qaida affiliated Al Nusra Front.

In recent weeks, Al Nusra commandeered U.S.-supplied weapons, such as anti-tank missiles, from moderate rebel groups.

The commander said now that the U.S. has stopped sending weapons and money, fighters desperate to feed their families will continue to join Nusra or the Islamic State. So far, as many as 800 to 1,000 fighters have left U.S.-backed rebel groups to join Nusra or the Islamic State, Razan Shalab Alsham, the field director for the Syria Emergency Task Force, told McClatchy.

Each fighter was receiving $150 per month, according to the commander.

According to McClatchy, the aid cutoff will not affect fighters belonging to two specific groups fighting to hold land near Allepo - Harakat Hazm and Nuruddin az Zinki.

A State Department representative reportedly told the commander that non-lethal food and medical supplied would for the most part continue to be sent, but the U.S. would not continue to pay the fighters.

The $1 trillion omnibus federal spending bill currently awaiting vote in U.S. Congress does however contain a provision to provide $500 million worth of weapons and other aid to Syrian rebels who have been properly vetted by U.S. forces, reported Breitbart.

A senior State Department official told lawmakers on Wednesday that a program to train and equip 5,000 additional Syrian opposition rebels will begin in March and take one year to be fully completed, according to The Hill.

Amnesty International issued a statement on Monday reminding U.S. officials to be cautious when supplying weapons to rebels in Syria and Iraq

"The U.S. Congress risks supplying fresh weapons to forces and armed groups with terrible human rights records in Iraq and Syria if it approves Obama administration proposals to waive human rights screening requirements on military aid," the group said in a statement.

"If approved, these new legislative proposals could simply open the floodgates, putting more weapons into the hands of armed groups alleged to have committed serious human rights abuses in both Iraq and Syria," said Sunjeev Bery, Advocacy Director, Middle East North Africa at Amnesty International USA.