Bush.
The Senate vote was passed by 65 votes to 34, a day after approval by the House of Representatives.
Prior to the lower house vote, Mr Bush personally appealed to lawmakers on Capitol Hill for swift passage of the legislation.
In a statement, the President welcomed the vote, saying the legislation would "provide our men and women in uniform with the necessary resources to protect our country and win the 'war on terror.'”
"As our troops risk their lives to fight terrorism, this bill will ensure they are prepared to defeat today's enemies and address tomorrow's threats," he said.
Political battleground
The legislation had become a major battleground in the national debate, pitting measures to safeguard the country from terrorism against the need to protect civil liberties, just weeks ahead of November legislative elections.
Republican Senator John McCain said the bill was a compromise between competing interests, but one which, crucially, maintained the US commitment to adhere to the Geneva Conventions governing the treatment of foreign combatants.
The measure was drafted in response to a US Supreme Court ruling in June that Bush had overstepped his powers and breached the Geneva Conventions by setting up special war crimes tribunals for "war on terror" suspects.
The sweeping legislation sets guidelines for interrogating suspected terrorists and would send several hundred inmates held at the US naval base in Guantanamo Bay, Cuba to trial after years of detention.
Most Democrats opposed the plan, seeing it as violating US principles and values by prosecuting terrorists without affording the due process allowed most defendants in the US criminal justice system.
Since the opening of a US detention camp in Guantanamo Bay, Cuba, in 2001, after the September 11 terror attacks, not one of the several hundred prisoners held there has been afforded a trial.
The draft law authorizes special military tribunals to prosecute the
Guantanamo detainees, allows for secret CIA-run prisons and forbids "cruel and unusual" punishment of detainees -- without further clarification of what falls in that category.
Critics have charged that Bush merely wants legal cover to allow interrogators to continue using "alternative" methods of questioning that reportedly include a simulated drowning technique known as "waterboarding," sleep deprivation and subjecting suspects to extreme temperatures.