Egyptian President Hosni Mubarak, weakened by a third day of police riots, today is more deeply than ever in the debt of Egypt's armed forces, which alone proved capable of quelling the embarrassing breakdown in the state security apparatus.

In many societies the Army's prompt action would seem the most natural of moves to preserve the state and its interests. But because of the growing vulnerability of Mubarak's four-year rule, such a debt has vast potential internal political implications.

Thus even before Defense Minister Abdel Halim Abu Ghazala's soldiers were able to smash the mutiny by police conscripts, Mubarak turned to hitherto marginal opposition politicians in an apparent bid to broaden his political support and use them, if necessary, as a counterweight to his ever more powerful defense minister. Abu Ghazala is widely viewed as one of the most influential leaders in Egypt and as a potential rival of Mubarak.

In turn, the politicians met with the president today, not so much in hopes of achieving a meaningful voice in policy as in fear that the defense minister might exert pressure on Mubarak to close down their tolerated opposition press.

But whatever the outcome of Mubarak's current balancing act, the past three days have weakened the regime's credibility at home and raised questions abroad about its stability.

For despite the high marks both here and abroad that Mubarak has been given for trying hard, this crisis has reinforced the president's image of being either unlucky or a bungler bereft of the kind of panache Egyptians expect of a leader.

The latest crisis comes only months after Mubarak was criticized by Washington for his handling of the Achille Lauro cruise ship saga, and at home and abroad for his handling of the Egyptair hijacking.

At the same time, there appears to be a widely held perception in the Arab world, whether accurate or not, that Abu Ghazala is a Washington favorite.

Even without such speculation, this crisis and those that came before it also serve indirectly to underline the Egyptian government's dependency on Washington, a dependency that many Egyptians say they find humiliating.

Notwithstanding the State Department's public expression of "confidence" in the Mubarak government and in "its ability to handle the situation," the mutiny has forced the Reagan administration to come to grips with the instability of the regime on which the United States has been spending $2 billion a year in aid.

To the extent that Mubarak does give the political opposition more than a token role in government, analysts say the price could be a further chilling in the already cold peace with Israel.

Whatever else divides them, opposition politicians agree in condemning those ties, which they hold responsible for Egypt's isolation in the Arab world.

Many Egyptians say they are convinced that crucial U.S. aid is primarily a lever to ensure that Mubarak's policy toward Israel stays within limits that, a number of recent incidents indicate, are increasingly unpalatable here.

The most striking involved the case of Suleiman Khater, an Egyptian policeman sentenced to life imprisonment at hard labor for killing seven Israeli tourists last October. He was found hanged in his jail cell last month, and while the government said he committed suicide, many Moslem fundamentalists have declared him a martyr and hero. He belonged to the same police force that mutinied this week.

With Mubarak caught between such forces, analysts are convinced that, at the least, Washington must consider dropping its recent efforts to tie $150 million in supplemental aid this year to further reductions in the $4 billion annual subsidies on food and other basic necessities.

Whatever forces may have been behind the mutiny -- and Communists and Moslem fundamentalists were charged with exploiting somewhat similar disturbances against the late president Anwar Sadat in 1977 -- the increasingly precarious economy, then as now, was thought to have sparked the disturbances.

The economy then was relatively healthy, thanks to the largesse of booming oil producers in the Persian Gulf. Now, Egypt owes at least $33 billion in foreign debt, according to the International Monetary Fund. IMF demands for stringent austerity measures were blamed for setting off the 1977 riots here as well as similar disturbances in the past two years in other prowestern Arab countries such as Morocco, Sudan and Tunisia.

But the deep cuts in current oil prices have not only shaved $750 million off government receipts from Egyptian crude production, but they also have slashed projected income from overseas workers' remittances and Suez Canal fees.

Even before this week's spectacle of burning luxury hotels near the Pyramids, tourism was suffering from last fall's terrorist takeover of the Achille Lauro and the storming of an Egyptian airliner in which more than 60 persons died.

One Egyptian intellectual said he was worried about Abu Ghazala's increasing importance and had deep misgivings about Mubarak's commitment to further democratization.

"It's an objective fact that the Army has preserved the regime," he said. "Now the key question is will this be endorsed, legitimized and institutionalized." He was expressing fears of a larger role for the military, which has dominated Egypt since the late president Gamal Abdel Nasser and his "free officers" overthrew King Farouk in 1952.