The Bush administration's conduct of foreign policy got a spirited defense Thursday from a person often considered to be the odd man out in making that policy.

Secretary of State Colin Powell (search) offered a sweeping appraisal of U.S. foreign policy, arguing that diplomacy has advanced U.S. interests and, in particular, helped Iraq.

"What is not there anymore is a horrible, dictatorial, filthy regime that did develop weapons of mass destruction, that used them against people, a regime that filled mass graves. It is gone. It is not coming back," Powell told reporters in a press briefing at the State Department.

Recent reports have questioned whether Saddam Hussein posed an immediate threat to U.S. national security and whether any weapons of mass destruction (search) will be found. Powell pointed to evidence that Saddam was hiding plans and matériel for weapons programs to keep his options open as reason for tearing down the regime.

"What he was waiting to do is see if he could break the will of the international community, get rid of any potential for future inspections and get back to his intentions, which were to have weapons of mass destruction. And he kept the infrastructure, he kept the programs intact," Powell said.

The secretary added that it was proper to look at some links between Iraq and Al Qaeda, even though no further evidence has turned up.

"I have not seen smoking-gun concrete evidence about the connection, but I think the possibility of such connections did exist and it was prudent to consider them at the time that we did," he said.

On Thursday, a liberal Washington think tank accused the administration of exaggerating the threat from Iraq, and argued that the United States should abolish its policy of conducting pre-emptive wars and should work with the United Nations on completing an inventory and history of Iraq's weapons program.

"It is unlikely that Iraq could have destroyed, hidden or sent out of the country the hundreds of tons of chemical and biological weapons, dozens of Scud missiles and facilities engaged in the ongoing production of chemical and biological weapons that officials claimed were present without the United States detecting some sign of this activity," said the report written by experts at the Carnegie Endowment for International Peace (search).

Powell, who was specifically named in the report, said the researchers at Carnegie did not say that they did not believe Saddam Hussein had the intent to threaten the United States.

"The fact of the matter is Iraq did have weapons of mass destruction and programs for weapons of mass destruction and used weapons of mass destruction against Iran and against their own people. That's a fact," he added. 

Former Defense Department official Richard Perle (search) also argued that it would be suicidal for the United States to decide its goals without the option for pre-emption.

"We can't get the U.N. to agree that terrorism is a threat such that we're justified in responding by taking action first, so-called pre-emption," Perle told Fox News. "According to the U.N., we have to wait until a 9/11 takes place before we can then respond. That's fine in theory but it won't save Americans."

But Perle has also criticized Powell in a recent book, saying the secretary is too dovish when it comes to foreign policy. Powell responded that the only person's view he worries about is that of President Bush.

Administration officials say they believe the use of force in Iraq has had a positive effect on the use of diplomacy elsewhere, convincing other nations that the United States was serious about its concerns.

That conclusion was drawn, in part, from recent pronouncements from Libya, which has agreed to give up all its weapons and open up the country to inspections.

"We saw Libya decide after many years that it wasn't worth the game, it wasn't worth the candle to continue to develop weapons of mass destruction," Powell said.

And in Iran, aggressive diplomacy in cooperation with the Europeans convinced the government there to agree to halt programs that could have produced nuclear weapons and to accept more intrusive inspections, Powell said. He added that the "humanitarian breakthrough," when Iran quickly accepted American aid after a devastating earthquake there, could mean a better future between two longtime adversaries.

Powell also looked to North Korea's recent suggestions that it will stop developing its nuclear weapons program while it waits for the next round of six-way negotiations. Powell said that while he was encouraged, none of North Korea's latest gestures could be taken seriously.

"What is absolutely essential for us to move forward, we need a clear statement from the North Koreans that they are prepared to bring these programs to a verifiable end," he said, adding that the United States will not make any concessions on North Korea until it agrees to give up its nuclear ambitions.

And in category of "the dog that didn't bark," Powell noted that a year ago people were worried about India and Pakistan having a nuclear war ... now they're about to open formal peace talks, an effort nurtured by the U.S.

Fox News' Jim Angle and Teri Schultz and The Associated Press contributed to this report.