He said this to the BBC in his first interview with a Western news organisation to be broadcast on Monday.
Al-Sadr, who led a six-month uprising last year in the Shia city of Najaf, said that the US "does not want confrontation".
"So I call upon other parties like the Iraqi army and the Iraqi police to exercise self-restraint with Iraqi people and not be provoked [by] them or the occupying forces as this isn't in the interest of Iraq," he said.
"I also call on the Iraqi people to exercise restraint and not get enmeshed in the plans of the West or plans of the occupation that wants to provoke them."
Al-Sadr: Foreign troops' presence
is the reason for problems in Iraq
But he added: "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 [George] Bush who said: 'If my country is occupied, I will fight'."
The presence of foreign troops was the reason for the current problems faced by Iraq, he argued.
"The occupation in itself is a problem. Iraq not being independent is the problem. And the other problems stem from that - from sectarianism to civil war. The entire American presence causes this," he charged.
Al-Sadr said he would not play any part in the democratic process while US-led troops remained in the country.
"I personally shall not interfere. I say that our constitution is the Quran and the Sunnah (tradition of the Prophet Muhammad) and I refuse any political role while the occupation is present."
"The occupation in itself is a problem. Iraq not being independent is the problem. And the other problems stem from that - from sectarianism to civil war. The entire American presence causes this"
The interview was to be broadcast only two days after three British soldiers were killed in Iraq by a roadside bomb, prompting the main opposition Conservative Party to demand the interview not be shown.
"Why are the BBC giving airtime to someone who at the best is on the fringes of what is acceptable?" Conservative defence spokesman Gerald Howarth said.