U.S. Ambassador to Nicaragua Anthony Cecil Eden Quainton yesterday refused to rule out the possibility of a naval quarantine aimed at reducing the "substantial" flow of arms and supplies to guerrillas in El Salvador.

His stance followed by a day U.S. Ambassador to the United Nations Jeane J. Kirkpatrick's suggestion that a demonstration of U.S. ability to interdict arms shipments on the high seas might be salutary.

Also yesterday, a top Pentagon official who requested anonymity said that the United States is "playing a little cat-and-mouse game" with the Nicaraguan government, and that a quarantine in the near future is "most unlikely."

Another top-ranking Pentagon official said yesterday that "the time is going to come" when a quarantine would begin if Nicaragua does not slow what the United States claims is a massive military buildup. However, he said there is no timetable for escalating planned U.S. naval maneuvers into a quarantine.

Appearing on "This Week With David Brinkley" (ABC, WJLA), Quainton was pressed to spell out U.S. goals in Nicaragua.

"Our policy," he said, "is not to topple the Sandinista government. Our policy is to try and modify its behavior in some substantial ways which are consistent with our interests and our vital security concerns throughout Central America."

Quainton said the United States wants to "get the Sandinistas to go back to the original goals of their revolution," which the ambassador said included "democracy . . . , a mixed economy and a truly nonaligned foreign policy."

In an interview Saturday on Cable News Network, Kirkpatrick said she thought it would be "useful to remind the Nicaraguans that they do not have a monopoly of force in the region."

"Are we showing them that the United States could . . . blockade Nicaragua?" Kirkpatrick was asked.

"Maybe," she replied. "Maybe we'll remind them of that. Maybe we're also doing something relevant to interdicting arms because they use--they do a lot of exporting arms into El Salvador by way of that Pacific corridor along the coast."

The blunt hints on a series of weekend television interviews were matched by growing expressions of alarm from several congressional Democrats. They protested that sending troops to Honduras for joint military exercises and stationing U.S. battleships, carriers and jet fighters off Nicaragua's coasts could violate the War Powers Act.

The Democrats--Sens. Daniel Patrick Moynihan (N.Y.) and Christopher J. Dodd (Conn.) and Rep. Michael D. Barnes (Md.)--also were critical of a pending Pentagon request to more than double the number of U.S. military advisers in El Salvador from its longstanding but unofficial lid of 55 to 125.

Pentagon officials yesterday confirmed that Defense Secretary Caspar W. Weinberger sent that recommendation to the White House last week. On Saturday, a White House spokesman said that such a request is not pending before President Reagan.

Reagan was asked by reporters upon his return yesterday to the White House from Camp David, "What about more advisers for El Salvador?" Waving off questions, he replied, "Not today."

One top Pentagon official yesterday said he believes that a quarantine is "most unlikely" in the near future. He said officials are leaving the possibility open for a reason.

"We're playing a little cat-and-mouse game with them, putting a little squeeze on, making them wonder what's going to happen next," the official said. "Ultimately, the idea is to convince them that allowing the El Salvador guerrillas to use Nicaragua for their headquarters for revolution is not a good idea if they want to keep their own damn revolution."

However, U.S. intelligence officials have concluded that the leftist Sandinista regime in Nicaragua faces little danger of being toppled without a much greater exercise of force, several sources indicated.

The latest National Intelligence Estimate on the troubled region, a composite study reflecting the views of the U.S. intelligence agencies, reportedly was completed June 30.

"It was interesting," one source said, "for the scenario it played out about where do you go from here. There are no good choices down the road."

Another source described it as blunt and confirmed that it had no dissenting footnotes.

Moynihan, who is vice chairman of the Senate Intelligence Committee, and Barnes, who is chairman of the House Foreign Affairs subcommittee on Western Hemisphere affairs, yesterday expressed similar conclusions, but without naming administration documents they had in mind.

In his appearance on "Face the Nation" (CBS, WDVM), Moynihan contended that the United States ought to get tough with the Soviet Union instead of fumbling around in Central America. He advocated an ultimatum centering on a wheat embargo and a western financial crackdown on Poland.

"The decisions about Nicaragua are made in Moscow, to the degree that they concern us," Moynihan said.

The United States, Moynihan said, should tell the Russians bluntly to "stop it. Stop sending arms to Nicaragua. Tell the Nicaraguans to get the headquarters of the El Salvador insurgents out of Managua. Don't even think about sending MiGs Soviet jet fighters from Cuba to Nicaragua. Get those Nicaraguans out of Bulgaria where they are training to fly those MiGs. Do that or else feed yourselves for the next 10 years, and find a way to pay for a bankrupt Poland, and as many other unpleasant things as we can imagine."

Barnes, who appeared on "Meet the Press" (NBC, WRC), and Dodd, who appeared on "This Week With David Brinkley," both argued that this is a bad time for the Reagan administration to make bellicose gestures, especially in the wake of a peace initiative proposed a week ago by the presidents of Mexico, Colombia, Panama and Venezuela, the "Contadora Group."

They proposed a 10-point plan to avert full-scale war, particularly between Nicaragua and U.S.-supported Honduras. Two days later, Nicaragua issued its own six-point plan, which, like the Contadora proposal, emphasized an end to foreign arms shipments into Central America and a ban on all foreign military installations.

Yesterday in Mexico City, the official newspaper El Nacional said that Cuban Premier Fidel Castro has thrown his support behind the Contadora initiative.

According to United Press International, Castro called for a "negotiated agreement" between the government in El Salvador and the guerrillas there, and for regional and bilateral talks directed at stemming the rising violence in Central America.

Barnes said he and Foreign Affairs Committee Chairman Clement J. Zablocki (D-Wis.) have been asking the Pentagon about the planned U.S.-Honduran military exercises, which administration officials have said could involve 5,000 military personnel during the next few months.

"When you're sending troops into the region for five months or six months, it's not a military exercise," Barnes said. "It's a deployment of military force into the region on a long-term basis."

As a result, Barnes said, "There is a serious issue of whether or not the War Powers Act should be invoked." That law requires the president to notify Congress when U.S. troops are sent into a hostile situation and allows lawmakers 60 days to order the troops brought home.

The law was invoked when Reagan sent a Marine Corps peace-keeping force to Lebanon, but Congress chose not to object. A recent Supreme Court ruling that invalidated the "legislative veto" provision in an unrelated law has raised questions about the validity of the War Powers Act, but several congressional leaders have said they still believe it is constitutional.

There are about 300 U.S. military advisers, radar operators and other personnel in Honduras now. During the planned joint exercises, thousands more would be sent in, but not all at once and only for a few weeks at a time, administration officials have said.

Barnes also repeated his disappointment with the makeup of a bipartisan commission to study Central American policy that Reagan named last week. The commission, to be headed by former secretary of state Henry A. Kissinger, does not include members who oppose Reagan's policies, Barnes said.

Kissinger is scheduled to meet with Reagan today. On Tuesday, the House is expected to take up a bill to cut off covert U.S. military and paramilitary support to the anti-Sandinista rebels.