Prominent Muslims fear Obama is preparing to step up efforts to help San'a fight al-Qaida by launching military intervention

A group of prominent Muslim clerics in Yemen warned today that they will call for jihad – holy war – if the US sends troops to fight al-Qaida in Yemen.

The group of 15 clergymen includes the highly influential Sheikh Abdul-Majid al-Zindani, whom the US has branded a spiritual mentor of Osama bin Laden but who is also courted by the Yemeni government.

The clerics' warning goes straight to the Yemeni government's dilemma in co-operating with Washington against an al-Qaida offshoot. In doing so, Yemen's weak regime must avoid upsetting al-Zindani and other radical Islamic figures whose support it needs to stay in power.

"If any foreign country insists on aggression and the invasion of the country or interference, in a military or security way, Muslim sons are duty bound to carry out jihad and fight the aggressors," the clerics said in a statement.

Barack Obama has said he does not plan to send US combat troops to Yemen, though Washington is increasing counterterrorism aid and training to Yemeni forces to fight al-Qaida in the Arabian Peninsula.

Concern about the growing capabilities of Yemen's al-Qaida offshoot increased after the failed attempt to bomb a US airliner shortly before it landed in Detroit on Christmas Day. US investigators say the Nigerian suspect in the failed attack told them he received training and instructions from al-Qaida in Yemen.

The group of clerics also said they believed an international conference on Yemen to be held on 27 January in London was intended to clear the way for the country's occupation by foreign nations. The conference is to be attended by the US and European countries.