The al-Qaida-linked Nusra Front has rejected the cessation of hostilities in Syria, instead urging insurgents to intensify attacks against President Bashar al-Assad and his allies.
Leader Abu Mohamad al-Golani said in an audio message played on Orient News TV on Friday that if Syria's war was not resolved, the consequences would spread to Sunni Muslims in other parts of the region.
"O soldiers of Sham (Syria), God honoured you with a great jihad on blessed land ... so strengthen your resolve and intensify your strikes, and do not let their planes and great numbers (of troops) scare you," he said.
The message came ahead of a cessation of hostilities due to take effect at midnight on Friday under a US-Russian plan, but which excluded Nusra Front and Islamic State fighters.
Golani said the truce plan was a plot which signalled the start of a political process that would keep the Assad government in power.
"The successful revolution is one which uproots the old regime with all its institutions," he said.
A victory for Alawites and Shi'ites - a reference to Assad and his allies including Iran - would mean a "shift of the battle to the Arabian Peninsula in less than a decade", he said.
Syria's main Saudi-backed opposition body has accepted the proposed cessation of hostilities.
Under the measure, which has not been signed by the Syrian warring parties themselves and is less binding than a formal ceasefire, the government and its enemies are expected to halt firing to allow aid to reach civilians and peace talks to begin.
The Damascus government and its Russian allies say they will not halt combat operations against Islamic State and Nusra Front.
Other rebels seen as moderates by the West say they fear this will be used to justify attacks on them.