In the face of the American public's cooling support for the Iraq war, President Bush's national address tonight - noting the first anniversary of the transfer of sovereignty to the new Iraqi government - will be the most important of his presidency.

The president - and the nation - have a tremendous amount at stake in the success of the Iraq mission, including stabilizing the Middle East, advancing freedom/democracy in the Muslim world and defeating Islamic terrorism.

Tonight the president must help an increasingly skeptical public and Congress understand the nature of the struggle we're in - and why we can't simply cut and run in the face of an aggressive terrorist insurgency.

If the president doesn't effectively make his case, calls will very likely increase in an already-wobbly Congress to curtail - or even end - U.S. involvement in Iraq before the job is completed.

That would be a tragic mistake - for Iraq, America and beyond.

The president must also soundly quash the idea of an early withdrawal from Iraq, now being tossed about on Capitol Hill. As Defense Secretary Don Rumsfeld said last week in testimony before the Senate, setting a deadline for withdrawal "would throw a lifeline to terrorists."

He's right. It's only common sense that the enemy - Sunni insurgents, foreign jihadists and Iranian and Syrian agents-of-influence - will wait out an American withdrawal to sink their teeth into Iraq.

Abandoning Iraq would be the equivalent of handing it over to al Qaeda terrorists or like extremists, providing them with a new beachhead in the Middle East. It could also result in Iraq becoming an Iranian-Syrian sphere of influence.

It would also teach the worst possible lessons - telling the Arab and Muslim world that we're not serious about Middle Eastern freedom and democracy, and proving to potential adversaries such as China, North Korea and Iran that America is a paper tiger.

The president must trumpet the (underreported) successes since Iraq's Independence Day: Eight million Iraqis braving death to vote in democratic elections, establishing a free government and drafting a new constitution is no small feat - and a good news story.

Of course, the president should "roger up" to the serious challenges that exist in dealing with the insurgency, while noting the progress in the training/equipping of Iraqi forces - without overselling their numbers or capability. Finally, he should articulate some of the steps he's going to take to advance the mission in Iraq in order to complete the transfer of power to the Iraqi government and bring our brave men and women home.

Here are some ideas:

First, the international community has promised Iraq a significant amount of aid money, having pledged $13 billion in a 2003 donor's conference. Shamefully, to date, only a small fraction of the promised assistance has been delivered.

Leaning on "deadbeat" donors to pay up would go a long way in training/equipping Iraqi security forces, reconstructing the country and putting people back to work - all good ways to crush the insurgency.

Second, one key to defeating the insurgency is to strip off the Sunni former regime elements from the rest (al Qaeda operatives and foreign jihadists) in a classic "divide and conquer" effort.

If the Sunni insurgents can be brought back into the political mainstream through negotiation, integration, amnesty or even exile, it will reduce the insurgency from as many as 20,000 to less than 5,000 members.

Third, hand in glove with wiping out the insurgency is continued progress on the political front. Iraq must still draft a constitution by Aug. 15, approve it in a national referendum by Oct. 15, and hold national elections by Dec. 15

A majority of Sunnis boycotted January's elections. But if the Iraqi state is to be fully representative of its people, the Sunnis must be brought in on the drafting of the constitution and made part of the mainstream political process ASAP.

Last Friday, President Bush welcomed Iraqi Prime Minister Ibrahim al Jaafari to the White House. After a closed-door meeting, Bush said, "Today we're at a critical moment in the history of this proud nation."

He was talking about Iraq, but the fact is that United States is also at a "critical moment" in its history. We are deeply involved in a Herculean effort to reshape the Middle East, "draining the swamp" of extremism and repression that feeds terrorism.

America must decide whether it will finish the job in Iraq, or let the region be plunged deeper into the darkness of the likes of Saddam Hussein, the Taliban and Osama bin Laden. President Bush should make that choice clear to the American people.

Peter Brookes is a Heritage Foundation senior fellow.