President Bush made a forceful argument Tuesday before the United Nations for a strong U.S. role in helping Iraq as it continues its transition away from the rule of Saddam Hussein.

"Over time, freedom will find a way," Bush said. "Freedom is finding a way in Afghanistan and in Iraq. We must continue to show our commitment to those nations."

Speaking for 24 minutes to a world body that didn't interrupt him with applause during his remarks, Bush said the United States still saw a role for the United Nations.

"The American people respect the people of the U.N. who stand for peace and human rights in every part of the world," he told the U.N. General Assembly (search) in New York City, held under extremely tight security.

Bush said the past three years were times of tragedy, but things are different now.

"Now we gather at a time of opportunity," he told the assembly. "The United Nations and my country share the deepest commitments … the equal value and dignity of every human life."

Bush's remarks offered a positive view of the world today, a world with less oppression, hunger and disease. His talk comes exactly six weeks before voters decide whether to re-elect him to a second term as president.

John Kerry, the Democrat seeking to oust Bush from the White House, said later Tuesday that Bush failed at the United Nations because he was "lecturing" the body instead of "leading" it.

"He does not have the credibility to lead the world. And he did not and will not offer the leadership in order to do what we need to do to protect our troops, to be successful and win the War on Terror in an effective way," the Massachusetts senator told reporters during his first full press conference since Aug. 9.

Bush not only hoped to soften his image overseas but also among critics at home. In his speech Tuesday before the United Nations, Bush made a firm defense of his decision to invade Iraq, in spite of escalating violence and mounting U.S. casualties 17 months after the president declared major combat operations over.

"We've witnessed the rise of democratic governments," he said. "They've taken root in modern societies and in traditional societies."

He predicted the continued escalation of terrorist attacks as the January elections in Iraq draw closer but said the solution "is not to retreat, but to prevail."

Unlike his speech to the United Nations last year, Bush did not devote the majority of his 35-minute address to Iraq and terrorism. He aimed to persuade U.S. voters and a skeptical global audience that there is more to his foreign policy than grim warnings about terror and aggressive use of U.S. military force.

His message was that the world is a better place thanks to his policies, and will get better still if nations band together to cooperate with his initiatives.

Bush reached out to the international organization to help with the reconstruction of Iraq.

"The people of Iraq have regained sovereignty," he said, noting that Ayad Allawi (search), the prime minister of Iraq's interim government, was among those attending the session.

"The U.N. and its member nations must respond to Prime Minister Allawi's request and do more to help build an Iraq that is secure, democratic, federal and free," Bush said. After his speech, Bush and Allawi met privately.

The call for action comes amid increasing scrutiny of the war in Iraq. Last week, U.N. Secretary-General Kofi Annan (search) said that from his point of view, the U.S.-led Iraq invasion was "illegal."

Ahead of Bush's speech Tuesday, Annan opened the meeting of the 191-nation gathering with a warning that "the rule of law" is at risk around the world.

"No one is above the law," Annan said. "Again and again, we see fundamental laws shamelessly disregarded — those that ordain respect for innocent life, for civilians, for the vulnerable — especially children," he said.

He condemned the taking and killing of hostages in Iraq, but also said Iraqi prisoners had been disgracefully abused, an implicit criticism of the U.S. treatment of detainees at Abu Ghraib (search) prison near Baghdad.

"Today, we must ask ourselves ... whether we are doing enough," Annan said Tuesday. "Let our generation not be found wanting."

Back in Washington, Iraq took center stage on the Senate floor. Sen. Wayne Allard, R-Colo., defended the president against the U.N.'s criticisms, saying the organization "should be grateful it now has the opportunity to bring democracy to the people of Iraq and Afghanistan."

But Democratic Sen. Tom Harkin of Iowa countered: "This administration has damaged our traditional alliances, undermined our moral authority.

"With our military tied down in Iraq ... we are less, not more secure, and more vulnerable, not less vulnerable," Harkin said.

In something of a pre-emptive strike, Kerry appeared at New York University on Monday to deliver a stinging attack on Bush's Iraq policy. Kerry, claiming the chaos in Iraq has made the United States less secure, urged the president to do a better job rallying allies, train Iraqi security forces, hasten reconstruction plans and ensure Iraqi elections are conducted on time.

From the campaign trail in New Hampshire, Bush dismissed Kerry's four-point plan as a proposal for "exactly what we're currently doing."

Bush's U.N. speech was sandwiched between meetings with world leaders — and a sit-down with Annan. It was an unusual burst of diplomacy for Bush, who has been keeping a punishing travel schedule to swing states as he seeks re-election.

Also Tuesday, besides his meeting with Allawi, Bush was meeting with the leaders of India, Pakistan, Afghanistan and Japan. Last year, Bush met with the heads of France and Germany — two of his harshest critics on Iraq. But he has no Europeans scheduled on this year's list of meetings, and aside from his host, Annan, no sharp critics of the Iraq war.

Finally, he was to visit with Mother Teresa's successor, Sister Nirmala.

That final meeting could help Bush with American Roman Catholics, a powerful voting bloc. It is also intended to send a signal about Bush's compassion for the poor.

For Bush, meeting Allawi marked a milestone of sorts. As the head of the fledgling government in Iraq, Allawi can help Bush put a human face on the reasons for the U.S. sacrifices thousands of miles away.

"He is a strong and determined leader," Bush said Monday in Derry, N.H. "He understands the stakes in this battle. I hope the American people will listen carefully to his assessment of the situation in his country."

Bush will host Allawi at the White House on Thursday, and the Iraqi leader will address Congress. Allawi speaks at the United Nations on Friday.

Bush's message to the world body mirrored the U.N.'s own agenda this year.

World leaders who arrived early focused on the failure to find $50 billion a year to help more than 1 billion people escape extreme poverty and start sharing global prosperity — and a report warned that if the money isn't found, the goals won't be met. They also discussed the need to ensure that millions of the world's poor don't get left behind by globalization.

FOX News' Catherine Donaldson-Evans and The Associated Press contributed to this report.