The ongoing withdrawal of American troops from Iraq could leave as few as 150 U.S. soldiers there after Dec. 31, when a 2008 pact says final withdrawals should be completed.

Or it could leave as many as 10,000 — who would remain indefinitely to help guarantee the security of the national government. What should concern Americans the most about the continuing negotiations over the final number is whether or not it is sufficient to keep Iraq a democracy — though admittedly a struggling one.

If the government falls, either to internal revolt or outside pressure, the entire U.S. enterprise there, which has cost about 4,500 American soldiers’ lives, will have been futile.

That question will be resolved in two places. The first is Washington, where the Obama administration says no final determination has yet been made. If 150 is the final number, they will train Iraqi troops in specialized areas such as maintenance and mechanized vehicle operations and tactics.

But rumbles reportedly coming from military commanders, filtered through sympathetic politicians, say that 150 is far too few to keep the security situation under control — which effectively admits that Iraqi soldiers and police are not yet capable of defeating domestic and foreign subversion.

It’s well known that Iran supplies terrorists and guerilla forces to attack Iraqi troops and civilian gatherings, as well as U.S. forces still in-country.

But the other place where decisions must be made about stay-behind troop levels is Baghdad, where Iraqi leaders face resistance from those who want all American troops gone and pressure from those who want a larger force to stay. Unless a new agreement is drawn up, nearly all troops will be gone in a few months, although the State Department is hiring about 5,000 private security guards to protect diplomats and civilian assistance groups.

Those guards will not provide military aid, however. Thus, Sen. John McCain took to the Senate floor recently to say that even 3,000 to 4,000 troops, another figure mentioned, would be too few to keep the situation stable.

While 10,000 troops are not enough to form an effective force in the field, they could elevate training levels for complicated weaponry and stiffen Iraqi forces in case of a major battle.

It would seem wise to use every means possible to persuade Iraqi leaders that their best interests are served by the maximum amount of security, not the minimum. The stakes are too high for anything less.