Britain may send troops to train Syrian rebels who are battling both Syrian president Bashar al-Assad’s forces and Islamic State (IS, formerly known as ISIS or ISIL) militants, the Independent reports. This follows a similar abortive attempt in 2011.

The news comes as the Pentagon announced plans for a US-led campaign to train rebels, with the ambition of garnering support from the international community. To take on IS extremists, officials say an infantry of up to 15,000 fighters may be needed.

Jordan is considered a likely location for such training, as the UK already holds a base there at which it trains that country’s military. Peshmerga Kurdish fighters and the Free Syrian Army, which are seen as “moderate” Syrian opposition rebels, would be trained by CIA-funded security contractors.

In support of a US-led campaign, ministers approved UK airstrikes against IS positions in northern Iraq last Friday. Most of the strikes by RAF Tornado jets have hit IS vehicles.

Prime Minister David Cameron has said repeatedly that Britain would not commit any boots on the ground in Iraq or Syria to battle IS. However, around 150 British military personnel are already said to be on the ground in Iraq, chiefly for advisory purposes, including members of the SAS and SBS.

This is not the first time the British government has sought to arm and train the Syrian opposition. In July this year, a BBC Newsnight investigation revealed that Britain had planned to train and equip a 100,000-strong rebel army in 2011 to overthrow Assad, before officials decided the plan was too risky.

General David Richards, then-Chief of the Defense Staff, drew up the secret ‘extract, equip, train’ plans.

As the UK government considers its role in the Pentagon’s rebel training plans, the vast and complex nature of factional opposition groups within Syria makes choosing dependable allies extremely difficult.

For instance, the Syrian-based militant group Al-Nusra Front, an offshoot of Al-Qaeda, has been fighting against IS in tandem with allegedly pro-Western groups. However, its positions have been targeted in US-led airstrikes.