UNITED NATIONS, SEPT. 15 -- This month's Security Council president, James Gbeho of Ghana, warned today that the council "would not tolerate" the imposition of an arms embargo against Iran at the present time, even though Tehran has not accepted the U.N. demand for a cease-fire in its war with Iraq.

Instead, Gbeho said, "there is no alternative" to a continuing dialogue with Tehran on a compromise that will satisfy Iran's domestic political needs while reaffirming the July 20 cease-fire resolution.

The Ghanaian ambassador spoke at a news forum sponsored by the U.N. Association of the United States before the return of Secretary General Javier Perez de Cuellar from a week-long trip to the Persian Gulf in search of a cease-fire.

He and other council members said they expected the secretary general to brief them Wednesday on his talks in Tehran and Baghdad, without recommending specific action. Iranian officials said publicly that they could consider a cease-fire, but only after the council names Iraq as the aggressor in the seven-year war.

Sources said Iran had offered to abide by a truce without saying so until after the formation of an independent commission to assign responsibility for the conflict. Iraq, the sources said, rejected this.

Despite the disagreement, Gbeho said many council members oppose an overt condemnation of Iraq as the aggressor. He suggested a compromise in which the council would "accept that Iraq aggressed, but would not say it in a way that will have Iraq dragged into court and forced to pay reparations." A possibility remains of having the cease-fire and the commission on defining the aggressor start simultaneously.

Western diplomats said that Ghana is the council member closest to Iran and that Gbeho is not a likely candidate for mediator. Gbeho denounced the United States, without naming it directly, for "spoiling for a war with Iran for its own domestic purposes."

American officials conceded Gbeho's assessment that the council remains reluctant to impose an embargo. Governments must first decide whether the new Iranian stance is a delaying tactic or an opening worth pursuing, the Americans said. Most nations are likely to wait until Iranian President Ali Khamenei addresses the U.N. General Assembly next Tuesday and meets officials of other governments who are gathering in New York for the session.

The Persian Gulf issue overshadowed today's ceremonial opening of the 42nd assembly, at which East Germany Deputy Foreign Minister Peter Florin was elected president.

On Monday, the 159 members are to begin hearing speeches by presidents, prime ministers and foreign ministers. President Reagan will make his sixth consecutive appearance at the assembly Monday.

In his annual report to the assembly, Perez de Cuellar cited the Persian Gulf as one example of a global trend toward increasing common ground among the major powers. There is, he said, "a commonly accepted interest in meeting successfully certain vital global challenges," including AIDS, drug trafficking and some arms control measures.

Although the United Nations is playing a larger role because of such "commonality," the secretary general said, it remains threatened by a financial crisis "of very damaging dimensions."

U.N. officials said actions on Capitol Hill this week could determine whether the United States, which provides one-quarter of the regular U.N. budget, restores the bulk of its payments to the organization, or continues to withhold more than half of the annual dues that it is obliged by treaty to pay.