President Reagan's recent criticism of the Central American peace process and his emphasis on supporting Nicaragua's contras have rekindled suspicion among some Central American officials and members of Congress that he does not want an accommodation with Nicaragua's Marxist leaders.

In recent days, doubts about Reagan's commitment to achieving a regional peace agreement have been voiced by Central American supporters of the plan put forward by Costa Rican President Oscar Arias and agreed to by five Central American presidents at an Aug. 7 meeting in Guatemala City.

Criticism also has come from House Speaker Jim Wright (D-Tex.), who helped to spark the Guatemala decision through the bipartisan peace initiative he and Reagan had proposed.

In an interview this week, Wright made clear that his arrangements with Reagan for a bipartisan approach have been strained close to the breaking point by what he regards as the administration's "active opposition" to the peace talks.

Central American diplomats were disappointed by the administration's spurning of their pleas not to raise the contra-aid issue before the Nov. 7 deadline set in Guatemala for working out a cease-fire and by Reagan's statements last weekend that the Arias plan is insufficient to force the "complete democratization" of Nicaragua.

Wright told reporters yesterday that his talks with Central American leaders recently have given him cause for cautious optimism that a cease-fire accord could be reached before Nov. 7.

White House press spokesman Marlin Fitzwater has denied that the administration is trying to force Nicaragua to reject an agreement by raising the negotiating stakes. He acknowledged continuing U.S. concern that the Arias plan does not ensure that Nicaragua will permit democratization and cut its military ties to communist countries. But he insisted that "this kind of criticism in no way is meant to be antagonistic to the plan or to indicate lack of support."

However, critics of the administration contend that recent comments by Reagan, as well as congressional testimony by Secretary of State George P. Shultz last week strongly suggest that the administration is unwilling to accept, under any conditions, a Marxist government in Central America.

In a U.S. News & World Report interview last week, Reagan said the contras must be supported until there is an agreement guaranteeing "complete democratization" of Nicaragua.

The president's critics say the implication is that the administration, which formerly sought to overthrow the Sandinistas by force, is offering them the alternative of agreeing at the bargaining table to accept a U.S.-dictated model of how Nicaragua should be governed.

However, Costa Rican Foreign Minister Rodrigo Madrigal Nieto, told reporters here last week that such a goal, however desirable to western democrats, ignores reality.

"The Sandinista leaders are Marxists," he said. "They make no secret of that. They are proud of it. They are not going to stand aside and turn the country into the kind of democracy the Reagan administration wants.

"However," Madrigal continued, "we believe the opportunity now exists where the Sandinistas will accept certain democratic measures called for in the Arias plan -- greater freedom of the press, independent political parties, guarantees of civil rights -- that will provide the beginnings of an infrastructure that cannot be easily dismantled and that can be built upon."

Other critics charge that the administration, with its insistence on "complete democratization," is attempting to hold Nicaragua to a higher standard than it applies to Washington's allies in the region. Of the four countries engaged with Nicaragua in the Arias plan, only Costa Rica has a long-established tradition of democracy.

The others -- El Salvador, Honduras and Guatemala -- have been ruled through most of their histories by military dictatorships. While they currently have democratically elected governments, the civilian leaders hold office only at the sufferance of the armed forces; and all three have been plagued by charges that the military and police have committed human-rights violations and other offenses against democratic rule.

Wright, in the interview, recalled that the Aug. 5 plan on which he collaborated with Reagan set forth three "legitimate concerns" of the United States: that there be no communist-bloc bases in Nicaragua, that Nicaragua pose no military or subversive threat to its neighbors and that the Nicaraguan government guarantee the rights and liberties set forth in its constitution, including "free, orderly elections."

However, Wright added that, at his insistence, this was followed by a paragraph written by him and stating in part: "Beyond this, the United States has no right to influence or determine the identity of the political leaders of Nicaragua nor the social and economic system of the country. These are matters wholly within the right of the Nicaraguan people."

Wright said he believes the Arias plan contains adequate provision for dealing with these concerns. He added: "It's no secret that I didn't vote for Ronald Reagan for president. But I'd take great exception to another government coming in and telling us to replace him with someone else and change our system to one that they like better."

Wright, who long was generally supportive of Reagan's Central America policies, said he is taking his current tack of "talking about peace and not about war or aid to the contras" because his contacts with a wide range of Central Americans, including Nicaraguans, have made him optimistic that the Sandinistas might be ready for an agreement that will resolve many U.S. regional concerns.

Shultz, in summing up the administration's position to Congress, sounded far more pessimistic. He said, "We cannot place our security interests at risk in the hope that positive internal changes will take place in Nicaragua . . . . It is simply not in our national interest to leave the Sandinista regime unconstrained by credible resistance forces on the basis of a hope or a premise."

In the past, such negative signals from Washington have been sufficient to scuttle moves toward a Central American peace accord. The question now is whether such observers as Wright and Madrigal are correct in saying that the process might be gathering a momentum that will make it more difficult for the administration to hold a peace agreement hostage to renewed contra aid or to Nicaraguan acceptance of the full package of U.S. "democratization" demands.