Memorial Day is a time when many Americans are wondering how long U.S. troops will be in Iraq.

Two Memorial Days ago, just after Baghdad fell, few thought 140,000 American soldiers would still be bogged down in Iraq today, with casualties mounting. The training of Iraqi security forces is dragging, and U.S. military commanders have been making sober predictions about how long the troops will remain there. One told the New York Times last week that U.S. involvement could last “many years.”

A recent NBC/Wall Street Journal Poll found that 53 percent of Americans would like to see the number of troops in Iraq cut; 40 percent want to maintain the current number.

Let me suggest a different way of looking at how long U.S. forces must stay in Iraq.

I think the answer rests with the Iraqis themselves.

What do I mean?

U.S. troops are stuck in Iraq because an insurgency is paralyzing the country. That insurgency grew in large part because of gross mistakes by top Pentagon civilians who misplanned and mismanaged the postwar. But if U.S. troops pulled out now, the country would collapse into civil war and chaos; it would become more of a magnet for terrorists.

Yet the key to ending this insurgency lies not with U.S. military efforts. It lies instead with the political strategy of newly elected Iraqi leaders. Only they have the power – with U.S. help – to divide the insurgents and isolate those who won’t lay down their arms.

Iraq is not Vietnam. The insurgency is mostly made up of Sunni Arabs, the 20 percent of Iraqis who held power under Saddam Hussein. They cannot defeat the 80 percent of Iraqis who are Shiite Arabs or non-Arab Kurds, but they can keep the country in turmoil.

Some insurgents are former Baathist supporters of Saddam who hope for a comeback; some are radical clerics. Some are Sunni officers angry at the U.S. abolition of the Iraqi army, or Sunni tribal leaders who used to be paid off by Saddam and are bitter that U.S. officials ignored them. Some are POIs (“p—ed-off Iraqis”), in the vernacular of some U.S. officials: Sunnis seeking vengeance for relatives killed by U.S. forces, or those who fear they have no future in an Iraq dominated by Shiites or Kurds.

To quell the insurgency, Iraqi’s Shiite-led government must split the Sunnis, convincing key leaders they have a future in the new order. Shiite officials are trying to do this, even though most Sunnis boycotted the January elections, and thus have few representatives in the new parliament.

Most important is the Shiite effort to get Sunnis involved in the drafting of a new Iraqi constitution. In Baghdad in January, I interviewed Homam Hamoodi, the Shiite cleric who is now chairman of the parliamentary constitutional committee. He told me: “By this constitution we hope every Iraqi will have his legal and national rights and real identity. We do not want a religiously or ethnically divided country.”

The Shiite leadership is holding a series of meetings with key Sunnis, urging them to hold caucuses around the country to pick representatives for the constitutional committee. Shiites hope such political participation will split moderate Sunnis from die-hard insurgents.

But fear and mistrust divide the two communities. Some Sunnis regard Shiite Muslims – who believe in a different line of succession to the Prophet Muhammad – as infidels. The language used by some educated Sunnis to refer to Shiites sounds like 1950s Ku Klux Klanners talking about blacks.

Where then lies the role for U.S. troops?

Even as Shiites woo Sunni leaders, insurgents are trying to undercut those political efforts. They target Shiite mosques and civilians, trying to provoke ethnic slaughter. Shiite clerics preach firmly against revenge, but it may become hard to hold some of their flock back.

Iraqi officials fear that if U.S. troops leave prematurely, the government won’t have the means to repel the insurgents. Senior Shiite leaders say the United States made a big mistake in disbanding the Iraqi army, rather than vetting and reshaping its units. Progress in building a new Iraqi army is slow. The sweep against Baghdad insurgents this week will test its mettle, but more time for training is needed.

“If the United States pulls out too fast, there will be chaos and revenge-seeking and maybe outside intervention,” I was told in January by Ibrahim al-Jaafari, now the new Iraqi prime minister.

“The United States promised it would remove the regime and stabilize the Iraqi situation. So it would be a betrayal of that promise” if they left prematurely.

In other words, Iraqi leaders need more time to isolate the Sunni hard core and motivate their fighting forces. That makes the U.S. presence dependent on the political skills of new Iraqi leaders. Wish them luck!