Syrian President Bashar al-Assad denied media reports on Friday that his ally Russia had drawn up a new constitution for his country and presented it to his government as part of international efforts to end the long conflict.

Lebanese daily al-Akhbar had reported on Tuesday that Russia had finished drafting a constitution which would remove many of the president's powers and set up a more decentralised government, both possible concessions to rebel groups fighting Assad.

"No draft constitution has been shown to the Syrian Arab Republic. Everything which has been said in the media about this subject is totally untrue," a statement on the Syrian Presidency's official Facebook page said.

"Any new future constitution for Syria will not be presented from abroad, but will be entirely Syrian: discussed and agreed upon by Syrians themselves and after that put to a referendum. Anything else would be worthless and meaningless," the statement added.

Bloomberg reported last month that Russia, which supports Assad, and the United States, which mediates on behalf of the Syrian opposition, were working on a draft constitution together.

A peace plan endorsed by the U.N. Security Council in December called for a Syrian-led transition process that establishes "credible, inclusive and non-sectarian governance", a new constitution, and free, fair elections within 18 months.