Blogger Andrew Sullivan has likened torture to a cancer on America’s democracy, that “metastasizes quickly and poisons everything it touches.”

Today’s Washington Post reports that “European prosecutors are likely to investigate CIA and Bush administration officials on suspicion of violating an international ban on torture if they are not held legally accountable at home, according to U.N. officials and human rights lawyers.” This has the potential to cause a great deal of tension in trans-Atlantic relations.

Leaders in the United States remain largely unaware of the political pressures on their European counter-parts. But anger in Europe at torture and the use of “black sites” in Europe combined with the political pressure from human rights groups creates a powerful dynamic for action.

First, if the United States fails to cooperate with these investigations, it raises the possibility of future difficulties in intelligence sharing and cooperation on criminal justice matters. Our failure to take active measures to investigate and punish torture taints our entire justice system, potentially causing problems on issues of extradition and sharing of evidence until the U.S. system is “clean.”

Second, uncertainty about the extent of our torture activities means that many current and former U.S. government officials may be in legal jeopardy if they travel to Europe. The challenge is somewhat muted during a Democratic administration but when the next Republican president is elected he or she will inevitably appoint large numbers of former mid-level Bush Administration officials who may be tainted by their role in authorizing and implementing torture. This is not just an individual problem but rather places at risk the ability of a future Republican administration to work with European allies on a wide range of issues.

Third, we are likely to face problems in the area of military cooperation as European militaries worry about cooperating with or serving under the command of officers who might be deemed war criminals. This clearly could pose problems for NATO.

The challenge is that our European allies are democratic states, responsive to political pressure at home, and with independent criminal justice systems that are bound by statute and treaty law. It is not a matter of simply reaching some sort of agreement to sweep it all under the rug with European leaders. European leaders may, in many cases, be constrained in their ability to look ahead rather than back as President Obama is urging.

Obama’s efforts to avoid a divisive and politicized fight at home over the punishment of Bush Administration officials for torture may lead to deep divides in the Atlantic alliance. The fact that none of the worst case scenarios has yet occurred is no reason to assume they won’t arise in the future. As long as we fail to excise the torture cancer from our system at home, it will hang like a Sword of Damocles over our relations with our closest and most important allies.

Dr. Bernard I. Finel, an Atlantic Council contributing editor,is a senior fellow at the American Security Project. An earlier version of this essay was published at ASP’s FlashPoint blog.