Israeli Prime Minister Shimon Peres today faced mounting pressure from his Labor Party and its allies to appoint a judicial inquiry commission to investigate an alleged cover-up of the 1984 beating deaths of two handcuffed Arab prisoners.

However, the Cabinet, fearing that such a move would cause a breakup of the 21-month-old coalition government, put off until later this week a vote on an inquiry as Israel's highest court prepared to consider the matter Monday and as the parliament prepared to debate four motions of no-confidence in the government over the issue.

What began as a sensitive security services scandal now appears to have turned into a partisan war of nerves. The rightist Likud faction of the coalition is threatening to force early parliamentary elections -- although it is just four months until a scheduled rotation in which Foreign Minister Yitzhak Shamir of the Likud is to become prime minister.

At the same time, Peres is trying to hold off leaders of his own party who appear to be seeking to scuttle the rotation.

Already, six of the nine Labor Party Cabinet ministers have publicly declared their support for an inquiry commission. A meeting Monday of the party's parliamentary caucus is expected to increase the pressure on Peres to authorize a probe into whether Shamir, who was then prime minister, tacitly approved a cover-up allegedly organized and directed by Avraham Shalom, who resigned Wednesday as chief of the Shin Bet secret security services.

Shalom, who was at the scene of the capture of the hijacked Israeli bus in the Gaza Strip, also has been accused of ordering the killing of the two captured Arab hijackers after they were led from the bus to a nearby field for interrogation. Security forces have said that they were urgently trying to question the hijackers about bombs believed to be on the bus.

Likud leaders accuse the Labor Party ministers of waging a vendetta against Shamir to prevent his rotation into the premiership on Oct. 25, without appearing to have reneged on the 1984 agreement establishing the "national unity" coalition.

Shalom resigned after President Chaim Herzog, with Cabinet approval, issued blanket pardons to the Shin Bet chief and three of his deputies, granting them immunity from prosecution for any crimes in connection with the affair.

Six months ago, three other former Shin Bet officials complained to then-attorney general Yitzhak Zamir that Shalom ordered the killing of the captive hijackers and then organized a cover-up involving perjury, suborning witnesses and falsifying evidence.

After unsuccessfully pressing Peres to approve a full police investigation of the alleged cover-up, Zamir was replaced as attorney general.

The Labor Party ministers met at Peres' home until 3 a.m. today, but Peres failed to change the positions of five Cabinet members favoring a probe: Energy Minister Moshe Shahal, Deputy Prime Minister Yitzhak Navon, Immigrant Absorption Minister Yaacov Tsur, Economics Minister Gad Yaacobi and Cabinet Minister Ezer Weizman. In addition, Communications Minister Amnon Rubenstein, of the Labor-allied Shinui Party, says he favors an inquiry commission.

Since three Labor Party ministers -- Defense Minister Yitzhak Rabin, Police Minister Haim Bar-Lev and Agriculture Minister Arye Nehamkin -- have sided with a unanimous Likud Bloc and its religious party allies against further investigation, it appeared unlikely that the proposals for an inquiry could have carried had they been put to a vote immediately.

However, Tsur, speaking to reporters after the Cabinet meeting, said the process of swaying other ministers to approve an inquiry had just begun. "This is a very critical week for the future of the government," he said.

While some ministers, including Rubenstein and Weizman, have hinted they might resign and force a Cabinet crisis if an inquiry panel is not approved, some Likud leaders said they were ready for early elections.

Ehud Olmert, a Likud spokesman, said, "These threats do not make any impression on me. . . . If the Labor Party wants to call for elections now, we are ready for elections. . . . We will ask the public opinion of Israel once and for all to pass its judgment and opinion about this."

Labor's Yaacobi responded, "I don't think a threat of going to general elections is a threat at all to the Labor Party. We are ready to do it."

Nonetheless, both Labor and Likud appeared to have little to gain by bringing down the coalition government and forcing elections.

In doing so, the Likud would expose Shamir to potentially embarrassing disclosures about his role during the months following the hijacking incident. Shalom, according to informed government sources, has said that his actions were carried out with the tacit approval of Shamir, who was then prime minister.

Peres is known to be concerned that his credibility would suffer if the Shin Bet affair were used to scuttle the rotation agreement. Peres also would likely be questioned by a judicial inquiry about reports that more than six months ago he rejected an appeal by former Shin Bet agents to approve an investigation of a cover-up.

Also, political analysts note, Peres would be forced into a campaign in which the Likud would present itself as patriotically having tried to defend the respected security services, while the Labor Party would be depicted as having placed partisan interests over national security.