THE AMERICAN government is starting to respond to the movement registered elsewhere in the quest for peace in Central America. Daniel Ortega went partway toward dealing with the contras, promising to negotiate a cease-fire through Bishop Obando y Bravo. Now Ronald Reagan has gone partway toward dealing with the Sandinistas, agreeing to sit with them at a table including the other four Central American states if serious cease-fire talks get under way. This situation represents progress and needs to be built on.

The Sandinistas' strategy is becoming clearer. It is to meet the hemispheric demand for granting a role to the contras by granting them a very limited role, as an indirect partner in cease-fire talks, and then to freeze them out of the country's subsequent political evolution. It is plain why they want to do this: the contras have a following and an appeal in Nicaragua, and the Sandinistas would rather face the many small fractious internal legal parties than a single, more broadly based popular movement. But of course there can be no real passage to democracy and reconciliation -- the necessary goals of the Arias plan -- if the peasant, church, middle-class and intellectual constituencies claimed by the contras are denied the political voice of their choice.

The American strategy is not so clear. As Secretary of State Shultz's speech yesterday made clear, the Reagan administration is wielding the Arias plan as a lever to pry the contras into a political position in which they can challenge and oust the Sandinistas at the polls. Hence the American reluctance to grant the Sandinistas the legitimizing boon of a direct one-on-one negotiation with Washington. Yet it is apparent that the American effort to keep the contras intact as a strong fighting force gives the Sandinistas the principal argument they use to fend off regional demands to open up their political system. By staying out of a direct negotiation with Managua, moreover, the United States deprives itself of the single forum in which basic U.S. security concerns can be addressed.

The essential consideration remains that the parties are responding to the stirring of a regional initiative. The Arias plan is not yet producing peace, and whether it will is far from sure. But where there was only one arena of struggle earlier -- the battlefield -- there now is a second: the negotiating table and the corridors leading up to it. That's where the focus must be.