Mr Bush was making the fourth of a series of speeches to defend his national security credentials ahead of November legislative elections that many in his Republican Party fear will be dominated by the unpopular war in Iraq.
For a second straight day, Mr Bush urged the US Congress to help derail court challenges to some of his most controversial anti-terrorism policies and touted what he described as major security improvements since the September 11, 2001 strikes.
"Many Americans look at these events and ask the same question: Five years after 9/11, are we safer? The answer is yes, America is safer," he said.
Invoking the spectre of those attacks days before five-year commemoration events, Bush said they showed how critical it was to keep nuclear, chemical and biological weapons out of the hands of terrorists and hostile governments.
"When we saw the damage the terrorists inflicted on 9/11, our thoughts quickly turned to the devastation that could have been caused with weapons of mass destruction," he told a supportive crowd.
"And now the world is uniting to send a clear message to the regime in Tehran: Iran must end its support of terror, it must stop defying its international obligations and it must not obtain a nuclear weapon," he said.
He also accused Tehran and Damascus of having "continued their support for terror and extremism" since the September 11 attacks, citing their support for the Shiite militia Hezbollah and its war with Israel.
Taliban ‘will fail’
Washington has called for UN Security Council sanctions on Iran for refusing to freeze sensitive nuclear activities. Tehran denies US allegations that it seeks atomic weapons, saying it seeks only to produce power for civilian use.
Mr Bush also urged the US Congress to pass legislation to safeguard his controversial wiretap program on US citizens.
He said his administration was appealing a federal ruling that the program is illegal.
Mr Bush, who said the war on terrorism must tackle potential threats pre-emptively, cited the US-led ouster of the Taliban Islamist militia in
Afghanistan in 2001 as a major early success and vowed that the latest uprising would fail.
"Five years later, Taliban and Al-Qaeda remnants are desperately trying to retake control of that country. They will fail," the president said as US forces faced their bloodiest year in Afghanistan since 2001.
"They will fail because the Afghan people have tasted freedom. They will fail because their vision is no match for a democracy accountable to its citizens. They will fail because they are no match for the military forces of a free Afghanistan, a NATO alliance and the United States of America," he said.
His comments came as supporters of the former Taliban regime have stepped up an insurgency in southern and eastern Afghanistan.
US officials say Afghan President Hamid Karzai's fragile government can barely control more than the capital, Kabul.
There are almost daily attacks against NATO and coalition forces, the Afghan army, police and non-governmental organizations.