BEIRUT, Lebanon — Insurgent commanders say that since Russia began air attacks in support of the Syrian government, they are receiving for the first time bountiful supplies of powerful American-made antitank missiles.
With the enhanced insurgent firepower and with Russia steadily raising the number of airstrikes against the government’s opponents, the Syrian conflict is edging closer to an all-out proxy war between the United States and Russia.
The increased levels of support have raised morale on both sides of the conflict, broadening war aims and hardening political positions, making a diplomatic settlement all the more unlikely.
The American-made TOW antitank missiles began arriving in the region in 2013, through a covert program run by the United States, Saudi Arabia and other allies to help certain C.I.A.-vetted insurgent groups battle the Syrian government.
The weapons are delivered to the field by American allies, but the United States approves their destination. That suggests that the newly steady battlefield supply has at least tacit American approval, now that Russian air power is backing President Bashar al-Assad
