West prepares to ban Syria's Islamist rebels on fears of growing influence

The United States and other Western countries are preparing to add a Syrian jihadist group to a list of banned terrorist organisations, amid fears that radical Islamists are increasingly dominating the armed opposition. The US state department is planning to add Jabhat al-Nusra, known in English as the Nusra Front, to its list of foreign terrorist groups, according to a Western diplomatic source.

The move comes as America, Britain and their European and Arab allies are compiling a new package of funding for the Syrian opposition, which is likely to be announced at a conference in Morocco next week. But on the ground in Syria, the Nusra Front and other extremist organisations are becoming a dominant force in the fight against president Bashar al-Assad.

Suicide attacks and car bombings — the preferred methods of these groups — are increasingly being used against some of the government's best-guarded strongholds. These tactics, which have also killed or maimed hundreds of civilians, are slowly shifting the balance of power against the regime. A senior member of the Nusra Front told The Daily Telegraph last week that the group was using suicide bombings and beheadings, while international jihadists — including volunteers from Britain — were fighting in the organisation. The aim was to create an Islamic state, not just in Syria, but across the Arab world.

Yasser al-Sibahi, who is based in Lebanon, controls the flow of arms and foreign fighters to a division of the Nusra Front run by his brother. A gold-framed image of Osama bin Laden is displayed on his laptop. He said that the Nusra Front sympathised with al-Qaeda's ideology, except for the sectarian hatred of Shia and Alawite Muslims and Christians.

After the terrorist attacks of September 11, the US enacted a law allowing the government to freeze the assets of any individuals or groups placed on an international terrorism list. One Western diplomatic source confirmed that they were "aware" of the State Department's move to place the organisation on the terrorist list. The source also said: "Britain is still looking at the options."

This may complicate the efforts to fund the Syrian opposition. Its allies are hoping to channel their support through the newly created Syrian National Coalition, a body that would send money to trusted contacts inside the country. But in a war that is increasingly chaotic, it may be difficult to stop money and weapons from falling into the wrong hands.

In northern Syria, where much of the territory is now rebel held, the influence of more moderate groups such as the Free Syrian Army is waning by comparison with the radical Islamists, who are often more disciplined and better-equipped. Videos have emerged of Nusra Front fighters capturing a succession of military bases in Deir al-Zour province. Other footage also shows the group's supporters carrying out mass executions of government loyalists.

"Their ferocity and fighting skills have made the jihadist Al-Nusra Front the dominant force in Aleppo now," one resident of the city said.

For the moment, Syria's jihadists are focused on what al-Qaeda call the "near enemy", namely the secular dictator running their country. Western governments, however, are concerned that their ambitions could widen.