Syria's foreign minister said on Monday that a decision by Western and Arab countries to arm the rebels posed a danger to peace talks and would prolong the two-year conflict.
Walid al-Moualem told a news conference in Damascus that the opposition had little hope of matching the Syrian army's strength despite a pledge by the states that make up the "Friends of Syria" to increase military support to the rebels.
"If they expect or fantasise that they can create a balance of power, I think they will need to wait years for that to happen," he said during the televised news conference.
Western and Arab countries as well as Turkey, who have thrown their weight behind the opposition, said their decision to arm the rebels was to rebalance the conflict that has killed more than 93,000 people, most of them civilians.
Syrian President Bashar al-Assad is widely seen as having gained momentum, seizing a strategic town near the Lebanese border which helps him cement control between the capital Damascus and his stronghold on the Mediterranean coast.
Moualem said that a move towards openly giving military support to the rebels would encourage terrorism and that radical Islamist groups linked to al Qaeda would benefit the most.
"The decision [at the Friends of Syria meeting] in Doha is dangerous ... because it aims to prolong the crisis, to extend the violence and the killing, and to encourage the terrorists to carry out their crimes," he said.
The United States and Russia are planning a "Geneva 2" peace conference between the opposition and Assad's government, but diplomatic deadlock has grown.
"They say [the arming decision] is to make the Geneva conference a success," the foreign minister said. "Arming the opposition will obstruct Geneva. Arming the opposition will kill more of our people."
"We head to Geneva not to hand over power to another side. Whoever on the other side imagines [this], I advise them not to go to Geneva," Moualem said. "We will head to Geneva to undertake a genuine partnership and broad-based government of national unity."
Syria's conflict began as peaceful protests against four decades of Assad family rule, but descended into a bloody civil war that has drawn in foreign fighters to both sides of the fight, increasing regional ethnic and sectarian tensions.
Syria's opposition, led mostly by the country's Sunni Muslim majority, has attracted foreign Islamist fighters. Shi'ites from Iraq and Lebanon have joined the fight on the side of Assad, who is from the minority Alawite sect, an offshoot of Shi'ite Islam.
Moualem told journalists that Syria wanted a ceasefire in order to hold talks at Geneva.
"We are insistent that if Geneva is held there must be a ceasefire, and we are ready to study mechanisms for observing it on the basis that neighbouring states abide, by halting training, arming and financing and sending them to Syrian territory," he said.