With scenes of violence and mayhem in Iraq replaced by more favorable images of the new Iraqi leaders taking charge and former president Saddam Hussein in the dock, top Bush administration officials launched an effort yesterday to ease the public's concern that the war has increased the threat of terrorism against the United States.

In speeches, briefings, interviews and an online chat, President Bush, Vice President Cheney, national security adviser Condoleezza Rice and others used the events surrounding this week's handover of political autonomy in Iraq to rebuild their case that Iraq is experiencing a "historic transformation" and Americans are safer as a result.

"After decades of rule by a brutal dictator, Iraq has been returned to its rightful owners, the people of Iraq," Cheney said in a speech in New Orleans, which made the case that Bush had reversed a terrorist threat that grew unchecked before he came to office. "America is safer, and the world is more secure, because Iraq and Afghanistan are now partners in the struggle against terror, instead of sanctuaries for terrorist networks."

Administration officials were clearly delighted by the developments in Iraq since Monday's handover; Bush watched some of the television footage of Hussein's combative arraignment in Iraq. While warning that more violence was certain to come, officials were hopeful that this week's events would begin to reverse the growing concerns about the Iraq war among the American public.

By 51 percent to 14 percent, Americans believe the threat of terrorism has increased rather than decreased since the invasion of Iraq, according to an NBC News-Wall Street Journal poll released yesterday. Thirty-four percent said the threat remained the same.

The impression that the Iraq war has hindered the fight against terrorism has some military concurrence. An Army War College study argued in January that the Bush administration had mishandled the war on terrorism by invading Iraq, which the study called a "a war-of-choice distraction from the war of necessity against al Qaeda."

Bush officials fanned out yesterday to make the case that the war in Iraq has broad international support and has improved the security of the United States.

Returning to the main justification for the Iraq war, Defense Secretary Donald H. Rumsfeld, in an interview released by the Pentagon, said forbidden chemical weapons were found in Iraq in recent days. Rumsfeld said the Polish defense minister told him this week "that his troops in Iraq had recently come across -- I've forgotten the number, but something like 16 or 17 -- warheads that contained sarin and mustard gas."

Rumsfeld added: "I have not seen them and I have not tested them, but they believe that they are correct that these, in fact, were undeclared chemical weapons."

Bush, in a ceremony swearing in John C. Danforth as U.S. ambassador to the United Nations, touted the agreement by NATO to train Iraqi security forces. Bush also said the United Nations -- with whom he has often feuded -- is serving "great purposes" in Iraq by helping to prepare for elections and a constitution.

Rice, in a chat on the White House Web site, said that although not safe, "we are safer today" than before Sept. 11, 2001.

Jim Wilkinson, who directs communications for the National Security Council, said it is important to keep "realistic expectations" that the assumption of sovereignty in Iraq will be rocky.

Still, Bush aides were jubilant yesterday after seeing the images of Hussein, with trim beard and open collar, in an Iraqi courtroom. "Today, this is case number one: the people of Iraq versus Saddam Hussein," White House press secretary Scott McClellan said.

Cheney, at the New Orleans D-Day Museum, delivered the most extensive defense of the administration's Iraq policy. "This week, only 15 months after the liberation of Iraq, we reached an important milestone, as the world witnessed the arrival of a free and sovereign Iraqi government," he said.

Countering the staff of the commission investigating the Sept. 11 attacks, which found no "collaborative relationship" between Hussein's Iraq and al Qaeda, Cheney renewed his accusation that they had "long-established ties." He listed several examples and stated: "In the early 1990s, Saddam had sent a brigadier general in the Iraqi intelligence service to Sudan to train al Qaeda in bombmaking and document forgery."

Senior intelligence officials said yesterday that they had no knowledge of this.

In an indication of the political significance of the wars against al Qaeda and Iraq, Cheney placed blame for the spread of terrorism on the Clinton administration.

"This," Cheney said, "was the situation when President Bush and I came to office: a world where terrorists were emboldened by years of being able to strike us with impunity, where unprecedented new attacks were being planned, where outlaw regimes provided terrorists sanctuary without cost or consequence."

The campaign of Bush's Democratic challenger, Sen. John F. Kerry, said Cheney's speech showed that Bush's campaign is "running scared" because Americans "are losing confidence" in Bush's terrorism policies.

But Cheney spoke of the war as a triumph. "It is a historic transformation for that nation," he said, adding: "This is a proud moment for the United States, as well."

Staff writers Thomas E. Ricks and Walter Pincus contributed to this report.