Lights have been dimmed in the corridors of the American Embassy in Tokyo, spouses were left off the invitation list for an already down-sized Fourth of July reception in Cairo this year, high-ranking American diplomats in Tel Aviv now have to share newspapers, and in several countries, visiting U.S. diplomats have become involuntary house guests of embassy employes rather than staying in hotels.

The cutbacks are part of an effort by the State Department to prepare for an anticipated $84 million shortfall this fiscal year, dictated by congressional budget-shrinking actions. If it were nothing more than petty harassments like these, many American diplomats abroad say, they would probably just grumble and try to ride out yet another war on spending.

But this time, in the view of diplomats interviewed by Washington Post correspondents in 13 major foreign capitals, essential programs and activities also are being jettisoned or severely cut back, in moves that are likely to have a long-lasting detrimental effect on U.S. diplomacy and reporting from abroad.

The diplomats said the reductions are being felt especially in areas where the United States is in direct competition with beefed-up embassies of its superpower rival, the Soviet Union.

Besides the closing of two small embassies and 13 consulates, diplomats point to sharp cutbacks in areas such as travel, which have led American officials to pay their own way to what they considered essential conferences, left them heavily outnumbered by Soviet diplomats at others and, in London, forced the embassy to reduce its consular visits to dozens of Americans in British jails from once a month to four times a year.

Staff reductions have forced many political officers to take on the unfamiliar duties of economics officers, and vice versa, or even to double up as consular officers, issuing visas and passports.

As a result, many diplomats say they see a shrinking role abroad for the State Department. In India, for example, where the embassy faces a shortage of key science and commercial officers, one diplomat expressed concern that more and more of the traditional foreign policy responsibility is being shifted to the Defense Department, the Central Intelligence Agency and the National Security Agency -- where budgets seem to be more bountiful.

In Jordan, where only 30 percent of the American Embassy personnel are State Department officials, one diplomat complained that "there are only a few people we have left here who are the core of why the State Department has a mission here." He contended that "they can't cut more, squeeze this function more, without turning the embassy into a support service for other agencies."

A chief worry, U.S. officials abroad say, is that the Soviet Union, under the new activist policies of Mikhail Gorbachev -- and an apparently more generous budget for his diplomacy -- is positioning itself to outstrip the United States in key regions of the world.

In India, the world's second most populous nation, cutbacks have left the United States with only 96 professional diplomats and 260 support officials, while the Soviet diplomatic staff has grown to about 600. In West Germany, when the main opposition party, the Social Democrats, held its national convention in Nuremberg last year, the Soviet Embassy sent six Bonn-based diplomats as observers. The American Embassy, struggling with budget cuts, could afford to send only two.

"The Soviets are turning up all over the country, to talk at forums and panel discussions. We try to do as much as we can, but we are limited by lack of funds," a senior U.S. diplomat in Bonn said.

A strong undercurrent in American diplomats' discussion of the budget cuts is a bitterness toward Congress, which continues to impose heavy responsibilities on the embassies and whose visiting members, many diplomats complain, continue to expect first-class escort services from missions that they now have reduced to second-class size.Washington Post correspondents Karen DeYoung in London, Edward Cody in Paris, Robert J.McCartney in Bonn, Richard M. Weintraub in New Delhi, Glenn Frankel in Jerusalem, Loren Jenkins in Rome, Fred Hiatt in Tokyo and Celestine Bohlen in Moscow, and special correspondents elsewhere, contributed to this article.

"The same Congress that cuts our resources requires the same amount of reporting," a diplomat in Cairo complained, referring to annual reports ordered by Congress on subjects such as human rights and labor activities.

The embassy in Bonn tried to close the U.S. consulate in Duesseldorf because Congress provided no funds to operate it -- but Congress ordered that it be kept open. So now it is staffed only with maintenance personnel and a telephone operator who refers callers to Bonn.

"Now we'll have 15 pounds of money to do 20 pounds of work," Gerry Hutchell, spokesman at the U.S. Embassy in Manila, said of efforts to match shrunken budgets to duties. After an internal messenger service that moved mail and memos around his vast U.S. Embassy in London was dropped as a money-saving move, Ambassador Charles H. Price II grumbled, "I wish to hell they'd do that to Congress. They'd have a fit."

Price, a staunch Reaganite who insists Congress is to blame for his embassy's budget horrors, said he tried to anticipate the State Department's budget tightening with a cost-cutting drive that began two years ago. It has not been enough, however, and he said that the cuts now have reached the point where further ones still rumored would be "mind-bogglingly stupid."

Price has frozen the salaries of all local hires, who make up about half of the 800 London embassy workers. Official travel has been sharply reduced, and a political officer recently paid his own way to Brussels because he felt his job required that he attend the annual NATO conference there.

The London embassy, which issues about 700,000 tourist visas a year, has closed down a three-person "visa information desk" that answered queries by telephone and now simply sends form responses to written inquiries.

"The essential message we've been trying to transmit," Lawrence D. Russell, the embassy's counsellor for administrative affairs, said last week, "is that we've done all the pruning we can. The next step is going to affect more than public services" and will seriously impinge on the reporting and diplomatic functions that are at the heart of embassy duties.

A major casualty of the budget-cutting, at least for now, is a $300 million Voice of America radio transmitter that is to be built in Israel. Deputy Secretary of State John C. Whitehead last month blocked $50 million designated to begin the project, citing deep cuts in the State Department budget.

Israeli officials said they were told this week that about $28 million will be found somehow to begin construction. But U.S. diplomats in Israel say the affair has caused great embarrassment since Israel had agreed to accept the transmitter reluctantly, and only after President Reagan had personally requested it in a letter to then-prime minister Shimon Peres.

In Cairo, where the United States has its biggest foreign mission, a two-year austerity program begun in 1985 has slashed local spending by half and left the embassy "lean and mean," but with no reserve for further cuts, a diplomat said. Entertainment spending has been cut 10 percent and travel allowances more than 30 percent, and 150 local employes have been dropped.

Slashes in entertainment allowances have been especially painful in Japan, where the effect has been aggravated by a sharp drop in the value of the dollar. The result, one official in Tokyo said, is a tendency toward less contact with Japanese sources than there should be -- and to keep that much contact alive, the official said, "most officers are out of pocket $500 to $2,000 per year on representation expenses."

U.S. diplomats in Jordan also personally absorb much of the cost of dealing with sources, an embassy official said, and the embassy is in the third year of a ban on buying new furniture. Although the embassy in Amman has long worked a Sunday-Thursday week, as most embassies in Islamic countries do to match the local practice, it is considering switching to a Monday-Friday week to save on Sunday pay differentials, despite its obvious mismatch to the schedule of Jordanian officials.

A blissfully unbothered exception to pressures to reduce spending is the U.S. Embassy in Moscow, which has spent the past year trying to deal with the sudden pullout of all of its Soviet employes, a rash of security scandals and problems resulting from the Chernobyl nuclear disaster.

"Moscow is such a top priority to Washington these days that money is the least of our worries," one American diplomat there said.