Barack Obama
U.S. President Barack Obama speaks at the National Defense University in Washington - Reuters

US President Barack Obama has warned Syrian President Bashar al-Assad against the use of chemical weapons against his own people in Syria and will face "consequences" if he resorts to any such attempt.

Recent reports from the region suggest that the Assad regime is preparing to use chemical weapons against Syrians which the regime continues to deny.

"The world is watching. The use of chemical weapons is and would be totally unacceptable," said Obama during his remarks on nuclear non-proliferation at the National Defense University in Fort McNair.

"We've worked to keep weapons from spreading, whether it was nuclear material in Libya or chemical weapons in Syria. We simply cannot allow the 21st century to be darkened by the worst weapons of the 20th century."

Obama's comments came hours after US Secretary of State Hillary Clinton said Washington would take action if Assad decided to use the deadly weapons against his own people. The White House said the situation has put the administration on alert to prepare for contingency plans.

The Syrian foreign ministry spokesperson told state television: "Syria confirms repeatedly it will never, under any circumstances, use chemical weapons against its own people if such weapons exist."

Washington and other nations have frequently expressed concerns that Assad might resort to chemical weapons as the last desperate attempt to save his regime.

The Syrian rebels fighting against Assad during the 20-month uprising have upped their attacks and seized important territories.

An unnamed US official said the Syrian regime was mixing chemicals that could be made into deadly Sarin gas. "We've picked up several indications which lead us to believe that they're combining chemical precursors," said the official.

The chemical weapons arsenal of Syria is regarded as the largest stockpile in the Middle East.

A report by the thinktank Royal United Services Institute for Defence and Security estimated that nearly 75,000 troops wee required to safely dispose of the stockpile of chemical weapons in Syria.