Nicaragua's steady drift leftward in recent months has ''very nearly become intolerable'' in the view of some senior officials in the Reagan administration. These diplomats, who are close to those forming United States Latin America policy, indicate that countermeasures may be necessary at some point. ''Something has to be done and done soon,'' says one top Reagan official.
These sources decline to specify exactly what they have in mind beyond allusions to depriving Nicaragua of aid (Congress is currently considering a $33 .3 million Nicaraguan aid proposal) and of trying to isolate it diplomatically and perhaps even physically. And they go on to say that there will be no unilateral United States action - at least without prior consultation with Caribbean allies.
But as they give vent to their growing exasperation with developments in Nicaragua, citing both human-rights violations and Nicaragua's growing military link with Cuba, officials here say the ''frustration level'' has been reached.
Although this impatience has been quietly building up for some time, it is obvious that the Cuba link, together with the arrival of sizable quantities of Soviet arms, is the most worrisome part of the picture. Washington makes note also of recent unconfirmed reports of Cuban troops in El Salvador, with the assumption that any such troops got there via Nicaragua.
Such administration officials are also concerned over the human-rights situation. One says that an ''outrageous abuse of individual liberties'' is evident in Nicaragua.
They point particularly to the arrest of four leading private-sector businessmen and the subsequent sentencing of three of them to prison terms, and to the closing of the newspaper La Prensa for short periods on five occasions within the past three months.
In the view of these officials, the Sandinista leadership in Nicaragua ''is showing its true stripes'' and appears determined to establish a Marxist state in Nicaragua.
The view here is that the Sandinista promises of political and economic pluralism, made at the time of the Sandinista triumph over the Somoza government in July 1979, are being nudged aside as the Sandinista leadership moves closer to Cuba and the Soviet Union. The Reagan administration cites these factors:
* The presence of Cuban military advisers in Nicaragua - the precise number not known, but certainly more in number than US military missions in other Central American countries.
* The arrival during late 1980 and early 1981 of large quantities of Soviet arms and ammunition from Cuba with the consequent beefing of the new Nicaraguan Army to the point that it is probably the best-supplied army in Central America.
* The early-summer arrival of an estimated 100 Soviet T54 and T55 tanks, post-World War II models that, although somewhat outdated, are the largest such vehicles in any Central American nation.
The administration's concern over Nicaragua was conveyed late last week to a group of prominent Venezuelan political and business leaders, including government officials. They were in Washington for the second annual United States-Venezuela Policy Dialogue, sponsored by the Smithsonian Institution's Wilson Center.
Though sympathetic in some measure to the administration's concern and similarly worried about Nicaragua's Cuba link, the Venezuelans caution Washington against any unilateral action.
Venezuela has become somewhat disenchanted with the Sandinista leadership - and this disenchantment is linked to curbs on civil liberties. Nicaraguan Defense Minister Humberto Ortega Saavedra's recent statement that Sandinista enemies ''will be hanging along the roads and highways of the country'' did not ease Venezuelan concern.
It was that statement that prompted the Superior Council of Private Enterprise, the largest group of businessmen in Nicaragua, to accuse the Sandinista government of economic mismanagement and ''an undeniable Marxist-Leninist hue.'' That accusation in turn prompted the arrest of the four businessmen.