The Unite States Senate has passed a bill overhauling the rules on secret US government eavesdropping and granting immunity to telephone companies that helped listen in on Americans after the Sept. 11 terrorist attacks.

The bill's passage ends almost a year of political wrangling over eavesdropping rules.

Opponents to immunity argue that only in court would the full extent of the program be understood, and only a judge should decide whether the program broke the law.

Patrick Leahy, Senator for Iowa, expressed his disapproval of the bill.

"As it is now, the bill would have the effect of ensuring that this administration is never called to answer for its actions. Never held accountable in a court of law. I do not support a result that says the president of the United States, whoever he is, is above the law. And therefore, I don't support the bill unless it is amended."

Just under a third of the Senate, including presumptive Democratic presidential nominee Barack Obama, supported an amendment that would have stripped immunity from the bill.

But the White House had threatened to veto the bill unless it immunised companies from wiretapping lawsuits.