There's an old fable about the dangers of grasping at a nettle in a tentative way: that's when the prickles get you worst, so either stay away or grab it firmly.

That fable has come to my mind recently as I contemplate the unsatisfactory nature of the role America seems to be playing in the post-cold-war world. It is often said that we're the world's one remaining superpower, but paradoxically the disappearance of the only other world power that could threaten us has consigned us to a kind of self-inflicted impotence.

When our survival was at stake, our moves in the world expressed conviction. This conviction derived from our having at least sufficient consensus as a nation about what we were doing and why. With the disappearance of the Soviet Union, our truly vital interests are rarely endangered. This greater safety has brought an erosion of consensus of when, if at all, the United States should intervene in world crisis areas.

One option is not to intervene at all: our vital interests are not at stake, Secretary of State Baker said of the situation in Bosnia five years ago; we've got no dog in this fight, Senator Gramm said of the Iraqi involvement in the Kurdish battles in recent weeks.

The problem with this option is that in an age of global television news, the film footage reaches American living rooms, subjecting the American people to night after night of pictures of mass killings and rape camps and other horrendous practices of the criminals against humanity. Our vital interests might not be at stake, but our values surely are. An American leader who stands by and does nothing is soon under great pressure to set things right.

But if the leader of the free world tries to respond to those pressures, he will soon come up against the other part of Americans' feelings about our role in the world. Why should a single American soldier die in a part of the world where our vital interests are not threatened? With so many unmet needs at home, why should American treasure be spent on distant places tending to other people's business?

If the president does nothing, he loses politically for not standing up for our values. If he acts strongly enough to seriously advance those values, he loses for getting us entangled where we've got no business. Under these circumstances, it is no wonder that we are developing a pattern of taking half-way measures.

In Bosnia, we broker the Dayton Accords and put troops on the ground. But our troops end up protecting mostly their own safety rather than doing the more dangerous work of enforcing the accords. Our soldiers do not enforce the guarantee of free movement the accords call for. We go out of our way to avoid arresting the indicted Bosnian Serb war criminals, although the agreement requires their removal. To grasp that nettle firmly would make one of the parties angry with us, and then our mission could well entail real costs in blood.

In Iraq, where five years ago President Bush stopped short of removing the man he'd likened to Hitler, in order to avoid taking on more burden than would have been easily taken off, President Clinton now neither ignores Saddam's provocations nor responds with sufficient vigor to drive a real lesson home.

In each case, we are active enough with our gestures to appease the half of the publics' sentiment that declares that something should be done, and cautious enough in our actions not to run afoul of the public's desire to avoid sacrifice where our vital interests are not on the line.

Politically, it is a sensible course for our leadership. Globally, it entails the cost of debasing the currency of the word of the United States, for it is the nature of such half-way measures that we either do not mean what we say, or we lack the resolve to make what we say stick. Thus the voice of the only nation that might lead the world forward loses conviction, and ceases to compel serious attention.

It would be good if we could come to some real agreement on what our role will be in this still-new global situation. But it is difficult to envision how we might achieve such consensus.