Washington, Jul 24 (IANS/RIA Novosti): US President Barack Obama has warned the Syrian authorities of being held accountable if they decided to use their arsenal of chemical weapons.

Syrian Foreign Ministry said Monday that Syria may use chemical weapons against external aggression as the West is pushing for a possible military intervention in the country torn by violent clashes between troops loyal to President Bashar Al-Assad and opposition forces.

"Given the regime's stockpiles of chemical weapons, we will continue to make it clear to Assad and those around him that the world is watching and that they will be held accountable by the international community and the United States should they make the tragic mistake of using those weapons," said Obama.

He was addressing veterans in Nevada state's Reno county.

The European Union, meanwhile, approved a new set of sanctions against Syria Monday, including a tougher arms embargo, in response to the escalating violence in the country.

The new sanctions came as Syrian government troops continued their large-scale offensive to force rebels out of Damascus and the northern city of Aleppo.

Up to 17,000 people have been killed in clashes between Assad troops and opposition fighters since the beginning of the Syrian conflict 17 months ago, according to UN estimates based on accounts provided by Syrian activists.