President Reagan is leaning toward a scaled-down contra assistance package that would put all lethal aid for the Nicaraguan rebels in an escrow account pending the outcome of regional peace negotiations, a senior administration official said yesterday.

Meanwhile, in a personal letter to Reagan, Nicaraguan President Daniel Ortega called for "the immediate cessation of all support for the contras" and renewed his call for direct U.S.-Nicaraguan talks. Ortega said he was committed to "democratization" and that Nicaragua now allows "the full and unrestricted exercise of freedom of speech, debate and association."

Reagan administration officials rejected both Ortega's appeal and his statement that the Nicaraguan government is seriously democratizing.

The senior U.S. official who disclosed that the administration is moving toward the escrow approach said that "Sandinista thugs" had broken up a meeting of the democratic opposition in Managua on Friday when they tried to exercise freedom of assembly.

The official said that the U.S. government continues to believe that any meetings with Sandinista officials should occur "in the regional context," that is, with the four Central American democracies that joined last August with the leftist government of Nicaragua in promulgating a regional peace plan.

The official said that placing the lethal contra aid in an escrow account would improve the chances of winning congressional approval of the aid request, especially in the House, and demonstrate that Reagan was willing to take "an extra step for peace."

Asked about an escrow plan on the ABC News program "This Week With David Brinkley," House Speaker Jim Wright (D-Tex.) said, "If the president requests it, I'll consider it -- I think it's worthy of consideration." Wright who could hold the key to passage of any additional aid request for the contras, said he would be guided by the recommendations of the four Central American democracies as to whether the contras should receive further humanitarian aid.

The administration's move toward an escrow strategy is designed to appeal to a moderate bloc of 19 House Democrats who have urged the president to delay his aid request and, if he does not postpone it, limit it to nonlethal assistance. Senate Minority Leader Robert J. Dole (R-Kan.) also has called for postponing a vote on the issue.

Administration officials said yesterday that they have little choice on the timing of the request, which must be submitted by next Wednesday and voted on in the House on Feb. 3 under terms of a compromise included in the bipartisan budget package approved by Congress last month. If the House approves the measure, it will be voted on by the Senate the following day.

Preliminary vote counts by the White House show that any proposal containing lethal aid is likely to lose in the House. Senior White House officials believe the administration might be able to secure passage of a limited package of nonlethal aid, especially if such a proposal has regional support.

Officials said the aid package now under discussion would be submitted Wednesday, a day later than previously announced, and include about $40 million of nonlethal aid and $5 million of lethal aid that would be put in escrow.

Whether congressional approval to release the lethal aid would be needed was not made clear. Wright indicated on the ABC program that he would not want the determination to be made by the State Department.

Rep. David E. Bonior (D-Mich.), at the House Democrats' annual issues conference held at the Greenbrier resort in White Sulphur Springs, W.Va., called the escrow possibility "a gimmick to trigger a release of funds" to the contras by the administration and added that any humanitarian aid should "go through the Red Cross and not the {Central Intelligence Agency}."

Assistant Secretary of State Elliott Abrams, who has overseen the administration's contra policy, is widely distrusted in the House. Appearing on the same ABC program before Wright, Abrams scoffed at Democrats who oppose contra aid, and said "it's really crazy" to cut off assistance to the rebels after pressure exerted by them has prodded the Sandinistas into making concessions.

The matter of what the package of "nonlethal aid" contains could also be an issue. In its definition of nonlethal aid, the administration includes not only items such as food, clothing and shelter, but also such items as helicopters and spare parts to transfer supplies to the rebels. Administration officials say that the downing of a plane in Nicaragua yesterday that was supplying the rebels underscores the importance of providing a way to deliver food and other essential supplies.

In his letter to Reagan, Ortega said that if the United States and Nicaragua signed "verifiable bilateral accords," that guarantees its security, Nicaragua could "advance more quickly" to agreements with its neighbors limiting the size of the Sandinista army and dispensing with all foreign military advisers and foreign military bases in Central America. U.S. officials said they saw nothing new in this proposal.

The letter was delivered to the White House on Saturday and also to The Washington Post and The New York Times, embargoed for use on Monday. The U.S. official who commented on it said the timing of the letter's release was an example of Sandinista public relations skill in putting forth a "peace of the day proposal."

Staff writer Tom Kenworthy in White Sulphur Springs, W.Va., contributed to this report.