I invite your attention to two headlines in The Post concerning a policy position taken by Ian Smith, leader of the white minority regime in Rhodesia. The first, on Nov. 25: "Smith Offers to Accept 1-Man, 1-Vote Principle." The second, on Nov. 29: "U.S. Favors Smith's Move But Says It's Not Enough."

Think about it. Smith makes an offer that, if converted by negotiations into political reality, would make Rhodesia-Zimbabwe the single country in all of Africa with a government on the American model; that meets the basic demand of authentic and popular black nationalists within Rhodesia (they at once agreed to negotiate on it); that promises fulfillment of the Carter administration's wildest fantasies of bringing peaceful change, peace, prosperity, multiracialism and near-Jeffersonian democracy to a torn corner of the world.

Smith makes such an offer and we reply: It's not enough.

Now, Britain, the American partner in trying to negotiate transition to black majority rule in the former British colony, is at least back on the track of consistency. Earlier some black moderates feared that Britain was about to swing behind the guerrillas of the Patriotic Front, whose chosen route to power - until Smith's recent offer, the only route available - is war. But the actual offer found London reaffirming its backing for one-man, one-vote elections.

The United States, however, has guerriallas on its mind. It shrinks from endorsing any proposal that leaves the guerrillas on the outside. The interesting question is why.

In some officials I detect a personal respect for the dedication of the guerrillas and a tendency to measure their own dedication to liberty and justice by their readiness to credit the guerrillas' struggle for these ideals. There is also an awareness that sympathy for the guerrillas is useful to our diplomacy in parts of black Africa.

But I do not think the U.S. position is an ideological or radical-chic thing. Official thinking about the guerrillas is more pragmatic. The guerrillas have rejected Smith's new gambit because they know (and every knowledgeable observer agrees) that they stand to gain more power in the battlefield. The administration fears they will keep the war going even if a black elected government takes office. Therefore, the argument goes, to stop the war you must ensure the guerrillas at least some part of the power, even if they could not win it at the polls.

United Nations Ambassador Andrew Young observes that holding elections now in Rhodesia without the Front is like holding wartime elections in Vietnam without the Vietcong. Much might be said about this formulation. I would say merely that in Rhodesia, even if the Front chooses not to compete, the free participation of the great majority of other black nationalists would make the elections legitimate.

American officials keep underscoring that Rhodesian elections should be "internationally acceptable." How can one-man, one-vote elections not be? By "internationally acceptable" the administration seems to mean that the elections should satisfy those front-line states, notably Zambia and Mozambique, that sponsor the principal guerrilla groups. In other words, if Zambia and Mozambique don't like the results a fair election might bring in Rhodesia, changes should be made.

So it is that the United States, though it has been mulling the question over, has not managed to bring itself to ask the guerrillas to test Smith's sincerity by demanding to take part in the drafting of a new constitution and in elections.

Furthermore, the United States, by refusing to open diplomatic contact with Smith even in this new period of intense negotiations, continues to deprive itself of 1) the information it needs in order to develop a sensitive policy and 2) the opportunity to present its own views to Smith, and to the Salisbury-based black nationalists, in an effective direct and timely manner.

I can see why it's hard for the Carter administration, which has supported the guerrillas in direct political terms and in indirect material terms (by providing aid to the front-line states), to tell them now that they should be prepared to accept only that share of the power that their numbers, their moral stature as freedom fighters and their political skills can bring them. The guerrillas feel strongly that their sacrifices entitle them to more. Their supporters among the front-line states underline the point.

Yet the first American responsibility is to ensure a free political choice to the people of Zimbabwe. Whether the guerrillas will be up to attacking an elected black government as they have attacked Smith is at least questionable. The line between trying to bring the guerrillas into the political process, and inadvertently encouraging them to reject it, is very thin.

It would be grotesque if the result of our high-minded diplomatic intervention, undertaken to install black majority rule, were to help install black minority instead.