Free Syrian Army fighters carry their weapons as they stand on the outskirts of the northern Syrian town of al-Bab, Syria Feb. 4, 2017. Reuters

The CIA has frozen its assistance to opposition groups fighting to overthrow Syrian President Bashar Assad after the groups were assaulted by jihadist forces last month, according to U.S. and Syrian rebel sources, Reuters reported Tuesday. The military and financial support was cut without explanation, according to the Syrian opposition officials who said they expected the halt would be temporary.

One U.S. official called leaks of equipment to jihadist groups "a constant problem" and a contributing factor to the gradual pullback of Washington's support for Syrian opposition forces. Two unnamed U.S. officials close to the CIA-funded program to train and equip rebels said the sudden freeze had nothing to do with President Donald Trump taking office. Trump was a vocal critic of efforts by his predecessor, former President Barack Obama, to back Syrian rebel groups. Trump, along with Assad and Russian Vladimir Putin among others, have argued the strategy only bolstered the forces of more radical Islamist groups fighting in Syria, such as Tahrir al-Sham, formerly known as al-Qaeda's Nusra Front and Jabhat Fatah al-Sham after that, as well as the Islamic State group, also know as ISIS.

Trump has also said he would make fighting ISIS a priority of his campaign and his administration has expressed willingness to work with any country in tackling ISIS, including Russia. Assad has said Damascus would welcome U.S. troops to fight jihadist groups in the country only if the operation was directly coordinated with Moscow.

A series of strategic victories by the Syrian army have compelled some opposition groups to support peace talks with the government sponsored by Russia, Iran and Turkey in Kazakhstan. Parallel U.N.-backed talks were also scheduled to be held this week in Geneva after a coalition of Washington-backed rebel groups fighting under the banner of the Free Syrian Army were taken by surprise last month when rival, jihadist opposition groups attacked their positions. The ambush inflicted heavy casualties, shifted loyalties among militants and further diminished hopes of any reconciliation among forces that have attempted to overthrow Assad for nearly six years in a conflict that has killed hundreds of thousands of Syrians and displaced millions more.

Meanwhile, the Kurdish-dominated Syrian Democratic Forces, which have not reported any interruption in U.S. aid, moved against ISIS positions Tuesday in the disputed eastern city of Deir al-Zour, while the Russian-backed Syrian army and Turkish-backed Syrian rebels have maintained a cautious truce as both forces advance on the northwestern ISIS-held town of al-Bab.