In most respects Lebanon and Nicaragua are different countries in different parts of the world, with different problems for foes and friends. In one respect they are alike. They are alike in that the White House in Washington is no more capable of stating its purpose clearly toward Nicaragua than it was toward Lebanon. From that lack of clarity springs its continuing troubles with the Congress.
The stated purpose toward Lebanon was to help rebuild a unified and independent Lebanon. Congress was willing to go along with that purpose, and provided funds and authority for the presence of the Marines for that purpose.
But along the way the United States ceased to work toward a resolution of the differences among the several political factions in Lebanon. Such a resolution was essential to a reunified Lebanon. The US, instead of mediating among the factions, became a partisan of one faction - the Maronite Christians - and actually used American naval gunfire and aerial bombs against Druze and Shiite militia forces. This use of American weapons in the factional fighting in Lebanon had two effects. It prevented Druze and Shiite factions from improving their military positions. It made the US Marines the target of Druze and Shiite military action.
We know the rest of the story. The Marines were not there in sufficient strength to fight both Druze and Shiite forces backed by the Syrian Army. The Marines had to be reinforced massively, or withdrawn. Congress refused to reinforce massively. The Marines were withdrawn. That ended the exercise in Lebanon. The failure of US intervention in Lebanon was due to ambiguity about the purpose, due to declaring one purpose but trying to pursue a different and more expensive purpose.
Today a far larger US armed force is building up in Honduras, which lies conveniently between El Salvador and Nicaragua.
The avowed purpose of this buildup is to help the recognized government of El Salvador sustain itself against an armed rebellion and to put pressure on the recognized government of Nicaragua to refrain from aiding the rebels in El Salvador.
Congress has, if grudgingly, provided funds for the first goal, of sustaining the government in El Salvador. The support is grudging partly because of the Salvadorean regime's wretched civil rights record. Its ''death squads'' still operate. Those who killed American church women, and other Americans, have yet to be named, convicted, and punished. It is grudging also because Congress suspects a larger purpose than is yet avowed.
Spokesmen for the administration speak of the danger to US ''vital interests'' and of threats to the survival of non-Marxist regimes in the area. There are continuing hints that since US interests are said to be ''vital,'' it may be necessary to send Americans into combat.
Congress is reluctant to withhold funds from the cause of resisting ''communist expansion,'' but equally reluctant to find itself backing an actual war with US troops invading Nicaragua. One result is Congress voting or allowing funds for the avowed purpose of the administration but voting an overwhelming, but nonbinding, disapproval of the specific act of mining the harbors of Nicaragua.
Hypocritical is hardly too strong a word for the action of Congress. Ambiguous would be a kinder label to put on legislators who vote both disapproval and funds. But the ambiguity of the congressional reaction is a logical reaction to the uncertainty and ambiguity in the White House presentation of the case.
Does it truly intend only to pressure the government of Nicaragua into desisting from aiding the rebels in El Salvador?
Or is it intending to bring down that government in Nicaragua by any means, including the use of American forces in support of the Nicaraguan ''contras''? The size of American forces now in Honduras, the use of US reconnaissance planes over El Salvador, and the mining of the harbors of Nicaragua all point toward increasing commitment of US forces.
Ambiguity and lack of clarity of purpose led the Reagan administration into failure in Lebanon. Ambiguity about purpose has already led the Reagan administration into trouble with Congress over Nicaragua, and has led the Congress into equal ambiguity in its reaction.
No one can foresee the outcome of so much ambiguity.