President Reagan said yesterday the United States is ready to move promptly toward a showdown in the U.N. Security Council over sanctions to be applied against Iran for intransigence in the Persian Gulf war, according to administration officials.

Reagan's remarks came in a meeting with the Saudi Arabian foreign minister, Prince Saud Faisal, which dealt with the situation in the gulf and the Middle East peace process.

White House spokesman Marlin Fitzwater said after the meeting that Reagan assured Saud "that the United States is committed to a major effort this month while we serve as president of the Security Council" toward obtaining passage of the sanctions resolution.

Other sources said Reagan and Secretary of State George P. Shultz have ordered U.N. Ambassador Vernon A. Walters to move promptly toward a vote at the United Nations.

The Soviet Union, like the United States a permanent member of the Security Council and entitled to veto any moves there, has been delaying a showdown since September on grounds that the United Nations should continue negotiations with Iran before moving to the sanctions stage.

The main sanction being discussed is an international arms embargo.

Saud and the Saudi ambassador to the United States, Prince Bandar, made their case for Soviet approval of the sanctions in a visit to Moscow about 10 days ago. Saud said yesterday that he left Moscow believing the Soviets have become "more amenable" to proceeding with a U.N. resolution calling for sanctions against Iran.

A diplomatic source said informal discussions of a sanctions resolution at the United Nations are likely to accelerate before the end of this week, leading the way for the resolution to be brought up within the next several weeks.

Britain is reported to have dropped its objection to mentioning Iran by name in the proposed U.N. resolution.

Bringing such a measure up in the Security Council would require Japan and western European nations, which make extensive oil purchases from Iran, to take a position on sanctions against that government, a potentially uncomfortable position.

Saud said adoption of a sanctions resolution against Iran would be a milestone in the effort to end the 7-year-old war with Iraq. The Saudi foreign minister also contended that a strong international stand to end the gulf war could bring about an evolution in the position of the Tehran regime.