Nicaragua moderates feel pinch of Sandinista-US tensions

''Sometimes I feel like I'm in the middle of a sandwich, squeezed between the Sandinistas on the one side and the contra and invasion threats on the other.'' This view - of Alvin Guthrie, head of the politically moderate Confederation of Labor Unity, an opposition labor union better known as CUS - is shared by many of Nicaragua's more moderate opposition members.

These moderates want to help find a peaceful way out Nicaragua's national crisis, but they feel they cannot as long as the Sandinistas are intransigent in negotiations with the political opposition and as long as the Reagan administration sticks with what the moderates see as a new hard-line stand against the Sandinistas.

Talks between the Sandinistas and the Nicaraguan opposition have been going on since October in an attempt to work out a political pact. Such a pact - which involves agreement on a pluralist society and mixed economy in Nicaragua - would ensure the opposition a role in the political system and potentially reduce US criticism of the Sandinista government.

But the talks, at present called the National Dialogue, have run into difficulty in large part because of a deepening climate of tension created by intensified US pressure on the Sandinistas. This has aggravated an already deep mutual distrust between the Sandinistas and the opposition.

In a meeting with the opposition last week Carlos Nunez, the Sandinista directorate member who represents the Sandinistas in the talks, called for the group's normal agenda to be set aside and asked for the signing of a resolution condemning the ''policy of aggression'' of the Reagan administration.

The opposition was upset that a part of the agenda on which it hoped to win Sandinista concessions had been put aside. But it suggested it would sign a resolution if the document scolded both the Soviet Union and the United States. Specifically, it said it would agree to a resolution calling for an end to all superpower intervention in Central America.

The Sandinistas refused this counterproposal. And the talks ended with the moderate opposition, led by the Social Christian Party, issuing its own communiques rather than signing a resolution.

Sandinista leaders then mounted a barrage of verbal attacks on the opposition , accusing its leaders of letting themselves be manipulated by US rather than Nicaraguan patriotic interests.

Opposition leaders fear the Sandinistas are using the dialogue to obtain an opposition condemnation of Reagan policies. The Sandinistas could try to use such a condemnation to help legitimize their government in the world community, they say. What assurances, they ask, does the opposition have that the Sandinistas will make real concessions after they get such a condemnation?

These opposition members also point to what they call the aggressive rhetoric of Sandinista leaders as a sign of non-interest in real negotiations.

Some moderate opposition leaders think current US policies are undercutting the opposition's position in Nicaragua.

''US armed intervention here would be a disaster, and right now US threats are only creating a situation in which it is difficult to negotiate, and an atmosphere which is undercutting the National Dialogue,'' says Azucena Ferre, a leader of the Social Christian Party.

(The US has repeatedly denied that it plans to invade Nicaragua.)

Ms. Ferre is critical of the conditions under which Nicaragua's elections were held Nov. 4. But she argues that they represented something of an opening, as did, potentially, the National Dialogue. She does not think the US should be pressuring the Nicaraguan government as intensely as it now is.

''Why is it that when the Polish government relaxed its repression somewhat in the last year the Reagan administration rewarded it by restoring some trade, while when the Sandinistas moderate their policies the only response is a step-up in US pressure?'' she asks.

But the opposition has become increasingly divided over what approach to take toward the Sandinista government.

Many Western diplomatic and opposition political observers say the most fundamental division within the opposition is between the groups that look to a negotiated solution as a way out of their national crisis and others that basically are waiting for US military intervention to solve the problem. These last groups think negotiations are a waste of time.

Another great division is between the opposition parties that participated in the election - the Democratic Conservative Party, the Independent Liberal Party (which was on the ballot even though its presidential candidate, Virgilio Godoy, officially withdrew from the race) and others that are in the political system - and parties that did not participate.

The key group that did not participate is the Coordinadora - a coalition of political, business, and labor organizations - which itself is now split. The Social Christian and labors union members of the Coordinadora want to negotiate with the Sandinistas. COSEP (a businessmens' organization), the Social Democratic Party, and some others do not.

One left-wing opposition leader also says there is a curious symmetry between right-wing opposition leaders and some of the leaders of the radical leftist Prolonged Popular War faction of the Sandinistas. Both groups, he says, seem to want war. The right wing wants it because it thinks war would save it from the Sandinistas. And some leftists think a US invasion would help to spread the ''revolutionary struggle'' to other Central American countries, even to Honduras and Costa Rica.

Sandinista radicals believe that should US troops invade Nicaragua, the Sandinistas would go into the Nicaraguan mountains to carry on guerrilla warfare and later move into Honduras. They would hope to outwait US troops, since they say the US public would not have the stomach for years of guerrilla fighting here if the US did invade.