UNITED NATIONS -- The 15 Security Council members began consultations this week on taking further steps to enforce a cease-fire in the Iran-Iraq war after Iran's rejection of the council's July 20 cease-fire resolution.

But a number of delegates displayed reluctance to impose sanctions on Iran, as the United States has suggested and as the resolution, adopted unanimously, implied that the council would do if the resolution were disregarded by either of the warring countries.

The reluctance, diplomats said, stems from the interests of Iran's trading partners and arms suppliers, such as China, West Germany and Japan; from the caution of some Third World nations about taking punitive action against a fellow member of the nonaligned movement, and from Iran's success in defining the issue as a confrontation between Tehran and Washington.

In fact, the resolution was drawn up jointly by the permanent members of the council -- the United States, the Soviet Union, Britain, China and France -- at the urging of Secretary General Javier Perez de Cuellar, and its terms have been accepted by Iraq.

In its response to the resolution, delivered this week, Iran charged that the text was "formulated by the United States with the explicit intention of intervention in the Persian Gulf and the diversion of public opinion from the home front."

A covering letter sent by Foreign Minister Ali Akbar Velayati was withheld from publication by U.N. officials because of its harsh anti-American and anti-United Nations language.

The five-page reply made it clear that Iran rejects the Security Council as well as its resolution as a medium for ending the seven-year-old Persian Gulf war.

Tehran made it clear that before it will consider an end to the fighting, the council must condemn Iraq as the aggressor, determine the extent of reparations to be paid, call for the withdrawal of foreign forces from the Persian Gulf and condemn the United States for its "military provocations" there.

Perez de Cuellar has said that, in the light of the Iranian reply, the council must now provide "guidance, not more time."

The process is likely to be slow. West Germany, which sells weapons to Iran and buys oil from it, holds the rotating presidency of the council for the month of August and is stretching its pulse-taking of each of the other 14 members into next week. Simultaneously, the five permanent members have resumed meeting in private to seek common ground on a resolution increasing the pressure on Iran.

Their first session was held Wednesday, with the secretary general present.

Before the resolution was adopted July 20, the five agreed that some form of sanctions -- possibly an arms embargo -- would have to be considered in the event that either belligerent rejected a cease-fire.

But there was no agreement on what constitutes rejection, how long to wait, or on the specifics of U.N. sanctions.

China, particularly, appears reluctant to act because of its stance as champion of Third World interests, its opposition to superpower dominance of other nations and its arms sales to Iran.