UN Secretary General Ban Ki-moon has called for a halt in arms supplies to conflict parties in Syria, his spokesman Martin Nesirky said on Wednesday.

“The Secretary-General reiterated his opposition to the further militarization of the conflict and he called on all states to stop supplying arms to all sides in Syria,” Nesirky told journalists by phone from the Iranian capital Tehran, where Ban is attending a summit of the Non-Aligned Movement.

The secretary general has met with Iran’s Supreme Leader Imam Ali Khamenei and President Mahmoud Ahmadinejad, Nesirky also said.

Since it began with demonstrations against Assad’s regime in March 2011, the Syrian conflict has escalated into a full-scale civil war that has claimed up to 20,000 lives, according to estimates by various Syrian opposition groups.

The West has been pushing for Assad’s ouster, while Russia and China have said the Assad regime and the opposition are both to blame for the bloodshed.

Nesirky said Ban called on the Iranian leadership to “use Iran’s influence to impress upon the Syrian leadership the urgent need for the violence to stop and to create the condition for a credible dialogue and a genuine political process that meets the will of the Syrian people.”

The Soviet Union and then Russia have traditionally been major arms suppliers to Syria, supplying a wide range of weapons including air defense systems, missiles, tanks, aircraft and helicopters. A diplomatic row broke out earlier this year when the United States accused Russia of supplying new Mi-25 helicopter gunships to Damascus. Russia insisted the helicopters were being returned after being renovated under an existing contract, and said it would only supply defensive weapons to Syria that could not be used to attack civilian protesters.

Moscow then later said it was unilaterally suspending a contract to supply Syria with Yakovlev Yak-130 combat training jets until the situation there stabilized.