Bush told reporters at the White House yesterday that the program included safeguards to protect civil liberties, but he also repeatedly cited his responsibility to protect U.S. citizens.
He expressed concern that newspaper reports disclosing the wiretap program were compromising U.S. security.
"It was a shameful act for someone to disclose this very important program in a time of war," Bush said. "The fact that we're discussing this program is helping the enemy. You got to understand -- and I hope the American people understand -- there's still an enemy that would like to strike the United States of America, and they're very dangerous. And you know, the discussion about how we try to find them will enable them to adjust."
The wiretapping by the National Security Agency (NSA) has caused an outcry in Congress and demands for an investigation. The program covers communications between the United States and parties abroad suspected of links to the Al-Qaeda network.
Bush and other officials have said the program involved monitoring phone calls and e-mails of individuals in this country believed to be plotting with terrorists overseas. Such intercepts normally require a court warrant but Bush said authorities need the ability to act swiftly to respond to threats.
In last night's news conference, Bush also continued his praise of Iraq's parliamentary elections last week, in which more than 10 million Iraqis voted.
He called for patience and said U.S. officials would work with Iraqis to build a constitutionally protected democracy.
"This election does not mean the end of violence, but it is the beginning of something new: a constitutional democracy at the heart of the Middle East," Bush said. "And we will keep working toward our goal of a democratic Iraq that can govern itself, sustain itself and defend itself."
Bush repeated his defense of the decision to wage war on Iraq, saying Saddam Hussein posed a threat to the United States because of his capacity to revive weapons programs.
The president acknowledged that intelligence failures on Iraq made it especially important to ensure the credibility of information about Iran's nuclear intentions. Bush stressed the U.S. commitment at the moment to finding a diplomatic solution to the crisis over Iran's nuclear program.
"The best place to make the case now is still in the councils of government and convincing the EU-3 [Britain, France, and Germany], for example, to continue working the diplomatic angle," Bush said. "Of course, we want to this to be solved diplomatically, and we want the Iranians to hear a unified voice."
Bush said there should be universal concern about a possible nuclear-armed Iran, especially after hostile comments from the Iranian president directed at Israel.
If diplomatic efforts fail, Bush said Iran's case could be referred to the UN Security Council, which has the power to enforce sanctions. Iran says its nuclear program is only intended for peaceful energy uses.