The head of the United Rubber Workers accused the Carter administration yesterday of joining with several major corporations, including General Motors Corp., to block a tentative rubber industry contract that vastly exceeded the government's anti-inflation guidelines.

Government sources acknowledged that administration officials were on the telephone to rubber company executives last Thursday almost immediately after learning that the URW was claiming to have negotiated a guideline-busting settlement with Uniroyal Inc.

The proposed pact reportedly called for wage and benefit increases of about 40 percent over three years, far beyond the 7 percent a year, or 22.5 percent compounded over three years, that the guidelines allow.

"The message was that such an agreement was unacceptable," said one administration source. Whether government pressure was decisive, however, was unclear. "The pressure had already come from elsewhere . . . from industry," said another official.

Several government officials said they understood that General Motors, a major buyer of Uniroyal tires, had joined other rubber companies in pressing Uniroyal to back off. But a GM spokesman flatly denied any GM involvement, saying, "There's no truth to that at all . . . General Motors has no part in the rubber negotiations."

The charges and countercharges emerged as URW President Peter Bommarito and bargainers for Uniroyal met separately here with federal mediators in an attempt to lay the groundwork for resumed negotiations and to avoid a strike.

The URW, which is bargaining for 55,000 workers at Goodyear, Firestone, Uniroyal and Goodrich, singled out Uniroyal as its target for possible strike action before contracts with the four companies expired at midnight Friday. But the union postponed a strike to allow time for more negotiations.

Meanwhile, there were these other developments in labor negotiations:

Machinists at Eastern Airlines ratified a contract patterned after a 1978 settlement with Trans World Airways, which provides wage and benefit increases of about 40 percent over three years. The contract is apparently exempt from the guidelines because it is patterned after a pre-guideline settlement.

United Airlines, which has been strike-bound since April 1, resumed negotiations with its machinists in Denver. UAL machinists have twice rejected a contract based on the TWA pattern, and earlier this month submitted demands considerably in excess of the pattern. A spokesman for United, which has idled 28,000 employes and cancelled all flights through April 30, said "we don't expect any fast, dramatic resolution."

The Teamsters union reported it had reached agreement with three of four major steel-hauling bargaining groups, but some dissident steel haulers vowed to continue their 10-day strike despite a union order against interfering with firms that agreed to the new contract. Three stikers were shot early yesterday near Youngstown, Ohio, when they attempted to stop a truck and the driver pulled out a sawed-off shotgun, according to police.

In the rubber contract talks, head-to-head negotiations were expected to resume today. Uniroyal continued to say it was trying to stay within the guidelines, while Bommarito reiterated his opposition to them.

Uniroyal has denied that it ever had an agreement with the URW although the talks appeared close enough to a settlement last week to mobilize government officials into what amounted to a guideline-rescue operation. Bommarito said yesterday there was "no question" in his mind that the government, along the other rubber companies and General Motors, pressured Uniroyal to "renege."