The US is reinforcing its troops in Jordan to prepare for a possible spill-over of violence from neighbouring Syria.

Some 150 US military specialists were sent to Jordan last year, and defence secretary Chuck Hagel said he had ordered an army headquarters team to bolster the mission, bringing the total American presence to more than 200 troops.

"These personnel will continue to work alongside Jordanian Armed Forces to improve readiness and prepare for a number of scenarios," Mr Hagel said.

"The deployment of the troops is part of US-Jordanian military cooperation to boost the Jordanian armed forces in light of the deteriorating situation in Syria," Jordan's information minister Mohammad Momani told the AFP news agency.

The announcement came as Syria's president Bashar al-Assad said Western nations would suffer the consequences for what he said was their support for Al Qaeda militants in his country's civil war.

"The West has paid heavily for funding Al Qaeda in its early stages in Afghanistan," Mr Assad said.

"Today it is supporting it in Syria, Libya and other places, and will pay a heavy price later in the heart of Europe and the United States."

The extracts from the interview with a Syrian television station were published on the Syrian presidency's Facebook page.

Mr Assad was speaking a week after Syria's rebel Al-Nusra Front, one of the most effective rebel forces battling his troops, formally pledged allegiance to Al Qaeda leader Ayman al-Zawahri.

The United States has designated the Nusra Front a terrorist organisation.

The presence of militant Islamists in Syria's two-year conflict poses a quandary for Western powers who favour Mr Assad's overthrow, but are alarmed at the growing influence of the Islamists in Syria.

"The truth is, what is happening is that we are mainly facing extremist forces," Mr Assad said in the interview.

The United Nations says more than 70,000 people have been killed in Syria's conflict, which started as mainly peaceful protests two years ago but has evolved into a civil war.

AFP/Reuters