U.S. President Barack Obama on Wednesday decided to extend the existing sanctions on Syria for one year, citing the "unusual and extraordinary threat" posed by the Arab nation to U.S. national security.

In a notice to be published in the Federal Register and sent to Congress, the president stated that the actions and policies being pursued by the Syrian government "continue to pose an unusual and extraordinary threat to the national security, foreign policy and economy of the United States."

He accused Syria, among others, of obstructing the Lebanese government's ability to function effectively, pursuing chemical and biological weapons, and supporting terrorist organizations.

Syria is viewed as an ally of the Hezbollah militant group, which dominates the Lebanese government but is branded as a foreign terrorist organization by the United States and the European Union.

Obama also alleged that the Syrian government's "brutality and repression of its citizens" could yield "greater instability" throughout the region, as the country has been beset by violent unrest since mid-March 2011. He again urged Syrian President Bashar al-Assad to step down to make way for a political transition.

"I am continuing for one year the national emergency declared with respect to the actions of the government of Syria" beyond May 11, said Obama. The move extends the accompanying sanctions that were first imposed in 2004 and expanded time and again over the years to cover Assad and his top aides.