THE CURRENT FEUD between Amtrak and Congress was predictable, for several passenger routes were selected with an eye more on politics than economics. Now that Congress is in a penny-pinching mood, the conflict over which routes or trains will be dropped is intense.

Amtrak had asked for a $534-million subsidy to keep all trains operating at the present rate through next September. Amtrak President Paul Reistrup said last winter that he could live with the $500 million the Carter administration recommended. When Congress went under that figure, Amtrak threatened to curtail service in the Northeast. A congressional conference committee, calling Amtrak's bluff, then forbade it to curtail service, offered only a fraction of the additional money sought and suggested the gap be closed by eliminatiog the most unprofitable routes. Amtrak replies that selecting these routes and going through pre-closing hearings will take so much time it will either have to discontinue more trains than it wants or run out of money next summer.

It seems to us that everyone should go back to square one. Amtrak does have severe problems - some created for itself, some by congressional demands for particular trains and some inherent in any intercity railroad service. No doubt some Amtrak routes ought to be eliminated. The one from Chicago to Florida, which Amtrak has decided to discontinue, generated in fares only about one-third of tis operating costs.

But the fundamental question is: How much is intercity rail service worth to the country? The right answer is unlikely to surface under the kind of time pressure now building. Amtrak's subsidy is direct and easy to see; subsidies to other intercity transportation systems (buses, airplanes and automobiles) are not. When you add in the difference in energy efficiency of alternative systems, calculations become even more difficult. Congress has ordered the Department of Transportation to make a zero-base study of the whole railroad-passenger network by March 1. The nation can afford to pay Amtrak's bills until Congress has had a chance to see that study and make a comprehendsive, long-range policy decision based on it.