Compromise "almost seems impossible" between the Reagan administration and members of Congress determined to cut off covert U.S. aid to rebels against the Nicaraguan government, the chairman of the House Foreign Affairs Committee said yesterday.

At the same time, Chairman Clement J. Zablocki (D-Wis.) added, "we don't have the votes as of today" to pass a bill that would halt the CIA-backed aid.

As compromise negotiations continued, the House voted after a brief but bitter debate to hold a four-hour secret session on Tuesday to hear classified information on the Central American situation from members of the intelligence committee.

Members of Congress on both sides of the issue agreed that the closed-door discussion would be crucial in deciding the aid question, which is likely to come to a vote the following week.

House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) told reporters he expects "a very close vote" on the bill, sponsored by Zablocki and Rep. Edward P. Boland (D-Mass.). It would halt covert aid to Nicaraguan rebels and instead provide $80 million in open aid to friendly governments with guerrilla troubles of their own.

"The fundamental disagreement is whether you think the United States ought to be doing what we're doing" in providing covert aid, said Rep. Michael D. Barnes (D-Md.), chairman of the Foreign Affairs subcommittee on hemispheric affairs.

He agreed with Zablocki, saying there is "no sign of progress" toward a compromise measure that would provide congressional control of the covert aid while allowing it to continue.

Backing the aid-cutoff measure, Rep. William V. (Bill) Alexander Jr. (D-Ark.), the chief deputy majority whip, told the House that covert aid against the leftist Sandinista government of Nicaragua is "unworthy, unworkable . . . and undeserving of support."

He said reports in The Washington Post that the CIA plans to ask for authority to support a secret army of 12,000 to 15,000 rebels were "fairly accurate" and indicated that "the administration is poised to escalate a dangerous course of intervention in Central America."

The White House, the State Department and the CIA all declined to comment on the report. House Minority Leader Robert H. Michel (R-Ill.), leaving a meeting with President Reagan, told reporters that "those are not correct figures" and that he was "very shocked" at the story. "I know better," he said.

House Democrats earlier held what O'Neill called a "one-sided" caucus on the issue at the request of 50 Democrats led by William B. Richardson (N.M.), who told a reporter he wants "the party to take a stand" against secret aid and stand up to Reagan.

Richardson said that he attended 32 town meetings in New Mexico during the July recess and that, of 1,632 constituents, "not one of them supported the president." The administration has said lack of information is behind such lack of support and has begun an intensive effort to explain to the public what it sees as a growing communist threat in Central America led by the Soviet Union, Cuba and the leftist Sandinista government in Nicaragua.

Republicans urging continuation of covert aid to anti-Sandinista rebels are proposing that the Boland-Zablocki measure be modified to cut off aid only when the Sandinistas certify that their own aid to leftist rebels in El Salvador and elsewhere in the region has stopped.

This idea has become known as "symmetry," and Zablocki said versions of it are central to the four-part compromise proposal under discussion. The current talks began about 10 days ago and have included three meetings on Capitol Hill and at least one at the White House, Zablocki and Barnes said.

The other three parts would ban all aid aimed at overthrowing the Nicaraguan government, provide open aid to block gun-running elsewhere in the region and establish a blue-ribbon, bipartisan study commission to report in six months on what U.S. policy in the area should be.

All sides agreed that the position of Majority Leader James C. Wright Jr. (D-Tex.) could be crucial. Rep. William S. Broomfield (R-Mich.), senior Republican on the Foreign Affairs Committee, said Wright is "a key figure" in compromise negotiations because "he is trying to bridge the gap" between the parties.

Wright said yesterday that talks are continuing with administration officials "to seek some common ground and to narrow our differences." O'Neill noted, however, that he expects Wright to vote against covert aid, and a source close to Boland said he is confident of Wright's support.

In an interview, Nicaraguan Deputy Foreign Minister Victor Tinoco, here on a routine visit, said Reagan's policy toward Nicaragua would be the same even if there were no conflict in El Salvador. However, he added, "We have no problem discussing with any administration official the so-called responsibility of Nicaragua with regard to El Salvador."

He said Nicaraguan proposals for such talks had been rejected repeatedly, most recently by special presidential envoy Richard B. Stone.

"He said talks were not necessary because there was no threat to the United States by Nicaragua and no need for any dialogue with us," Tinoco said.

In a related matter, Rep. Stephen J. Solarz (D-N.Y.) collected 30 Democrats' signatures on a letter urging Reagan to withhold his certification, due Wednesday, that there has been progress on human rights and social reform in El Salvador.

The law requires that such certification be provided to Congress every six months for U.S. military aid to continue, but the letter argues that there has been no progress.

"All previous certifications have been justified in terms of a decline in the number of non-combatant deaths," Solarz said. "Now the number is up by a couple of hundred over last time." He said the figure represented a 10-percent increase over the estimated 2,000 civilian deaths reported by human rights groups in the first six months this year.

Also yesterday, the Organization of American States opened a special debate on Central America with a charge from Honduran Ambassador Roberto Martinez Ordonez that a Nicaraguan arms buildup threatens "a war without frontiers" in the region. He said Nicaragua had violated Honduran territory nearly 200 times during the last four years.

U.S. Ambassador J. William Middendorf offered "strong support" for Martinez's allegations, calling the military buildup in Nicaragua "alarming." Nicaraguan Ambassador Edgar Parrales faulted Honduras for regional tensions, saying Honduras lets anti-Sandinista rebels use its territory.

"When you play with fire, you get burned," he said.