There's one word President Obama uses a lot in his argument for tightly limiting U.S. military action in Iraq. The word is "lid."

"Our military is so effective that we can keep a lid on problems wherever we are, if we put enough personnel and resources into it," Obama told reporters Saturday morning.

"Our military is so capable, that if we put everything we have into it, we can keep a lid on a problem for a time," Obama told the New York Times in an interview published this weekend. His message to Iraqi leaders, Obama said, is: "We will be your partners, but…we're not sending a bunch of U.S. troops back on the ground to keep a lid on things."

"We certainly can't redeploy tens of thousands of U.S. troops to try to keep a lid on the problem if the people themselves don't want to solve it," Obama told CNN June 20.

"We're not going to allow ourselves to be dragged back into a situation in which, while we're there, we're keeping a lid on things," Obama said in a June 13 statement.

The view of the Iraqi situation behind the president's "lid" remarks is that the U.S. invasion of Iraq unleashed murderous sectarian forces that had been kept in check -- under a "lid" -- by the dictatorship of Saddam Hussein. After a period of chaos and great violence, which grew even with the presence of more than 100,000 U.S. troops, President George W. Bush sent a surge of even more troops into the country -- the peak number was 168,000 -- to put a new lid on Iraqi sectarianism. The surge succeeded, but later, when American forces left under an order from commander-in-chief Obama, the lid came off. Now murderous sectarian violence threatens the very existence of Iraq as a nation.

Yes, the United States could re-impose a lid on Iraqi sectarianism, Obama is saying, but only by taking extensive military action, which would certainly involve sending American ground troops back to the country. That is something the president will not do. Now, the question for Obama's critics is how many American troops would it take to put that lid back on Iraq, which might, or might not lead to a lasting solution to the problem of sectarian violence?