Zabihullah Mujahid said the Taliban, as rulers of Afghanistan, are ready to fully implement the 1972 Helmand River Treaty.
Under the treaty, Afghanistan is committed to sharing the water from the Helmand River with Iran and will supply 26 cubic meters of water per second, or 850 million cubic meters per annum.
A disagreement over the interpretation of a 1973 treaty between Iran and Afghanistan on water from the Helmand River has plagued relations between the two countries for decades.
Afghanistan started building a dam over the river in 1974, but war and related issues delayed completion until last year.
