At a news conference at the White House he said time is running out and the enemy will attack America again.
Mr Bush's comments come a day after a US Senate committee rejected his plan to relax standards on the treatment of "war on terror" suspects, instead backing a substitute bill offering greater rights protections to foreign detainees.
In a stinging rebuke to the US president, the Republican-led Senate Armed Services Committee voted 15 to nine in favour of a bill drafted by Republican chairman John Warner.
The approved legislation, which will now go to the full Senate, would ban abusive CIA interrogations and make it easier for terrorist suspects to defend themselves at trial.
Mr Bush’s plan, which would allow tougher questioning of detainees while protecting US interrogators from being prosecuted for war crimes, was earlier approved by a US House of Representatives panel.
President Bush praised the House Armed Services Committee for having passed his bill, which he called "a very important piece of legislation in a bipartisan fashion that will give us the tools and wherewithal to protect this country," he said.
Mr Bush then visited Capitol Hill to drum up additional support for his legislation.
But the Senate committee was convinced by Mr Warner's arguement that the president's bill could endanger future US prisoners of war and hurt America's standing in the world.
The Senate vote sets up difficult negotiations with House of Representative lawmakers and Bush administration officials over their differing versions, but Senator McCain said an accord was within reach.
"I think we see a compromise there so that we could prevent national security from being compromised, but yet still allow the defendant to be able to see some of the evidence against him," he said, speaking on CNN.
"What we are seeking is to make sure that the Geneva Conventions covering these circumstances are not changed, because if we amend the Geneva Conventions, then other nations will to their liking," which he said "could put American lives at risk."
President Bush’s plan would redefine which acts constitute war crimes, after the Supreme Court ruled in June that his existing court system established to prosecute terrorism suspects, like those held at Guantanamo Bay, was illegal and violated the international Geneva Conventions.
CIA techniques
The Senate bill would ban abusive techniques that the Bush administration doesn't consider torture, such as "water-boarding," which simulates drowning.
Although the US military has banned a long list of abusive interrogation tactics, the prohibitions don't apply to the CIA.
Mr Bush said CIA interrogators should have wide latitude when questioning terrorists, as long as they don't engage in torture.
"We have proposed legislation that will enable the Central Intelligence
Agency to be able to conduct a program to get information from high-value detainees in a lawful way," President Bush said.
"It is very important for the American people to understand that in order to protect this country we must be able to interrogate people who have information about future attacks," he said.
Secretary of State Condoleezza Rice, in a letter delivered to Senator Warner's committee, called the administration’s bill a "reasonable, good faith interpretation" that does attempt to take human rights concerns into account.
Republican opposition
The president's proposals were strongly opposed by three powerful Republican senators – Senator Warner, Lindsey Graham and John McCain-- who insist there must be no erosion in US compliance with international law governing the treatment of war detainees.
At a press conference on Wednesday, Senator Graham -- who is also a military lawyer -- denounced the White House proposal.
"It started with Abu Ghraib," he said, referring to the notorious Iraqi prison where US abuses were found.
"Are we going to start being the first country in the world that changes the Geneva Conventions so the secret police programs of those nations will be OK?"
The split in Republican ranks widened as former Secretary of State Colin Powell joined the dissidents against his former boss.
Mr Powell agreed with other retired senior military officers who contend that President Bush's approach undermines support for the war on terrorism and encourages abusive treatment of captured Americans.
Mr Powell sent a letter to Senator McCain condemning the administration's plan to change rules governing detainee treatment, which are covered under Article Three of the Geneva Conventions.
"I do not support such a step and believe it would be inconsistent with the
McCain amendment on torture, which I supported last year," Mr Powell wrote.
"The world is beginning to doubt the moral basis of our fight against terrorism. To redefine Common Article Three would add to those doubts," wrote Mr Powell, who is also ex-chairman of the Joint Chiefs of Staff.
But President Bush dismissed Mr Powell's remarks, saying "there's all kinds of letters coming out," and pointed out that a group of military lawyers sent a letter to the House and Senate Armed Services panels supporting the administration plan.
Republicans are caught in intra-party conflict over the legislation in the middle of the election season on which it plans to campaign on national security.