Cleric is defiant.
Moqtada al-Sadr, whose Mahdi army fought the United States in Najaf, urges Iraqis not to be provoked by the coalition "occupation".
But al-Sadr tells Newsnight: "Resistance is legitimate at all levels be it religious, intellectual and so on.
"The first person who would acknowledge this is the so-called American President Bush who said `if my country is occupied, I will fight'."
The interview comes after three British soldiers were killed in a roadside attack at Al Amarah over the weekend.
They came from the 1st Battalion, Staffordshire Regiment, based in Wiltshire and were patrol commander Second Lieutenant Richard Shearer, from Warwickshire, Privates Phillip Hewett, and Leon Spicer, both from Staffordshire.