Secretary of State George P. Shultz said yesterday the Reagan administration is moving at full speed so that by mid-July it can begin protecting former Kuwaiti oil tankers now flying the U.S. flag, despite calls in Congress to delay the plan.

Shultz said in a televised interview that he is "absolutely" opposed to delaying the new U.S. naval steps in the Persian Gulf. He called such a postponement "a very bad thing to do from the standpoint of the United States" and said the reflagging and protection of Kuwaiti tankers is "a sensible thing to do."

Shultz declared on NBC's "Meet the Press" that "the worst thing that can happen to the United States is to be sort of pushed out of the Persian Gulf." He also said that "the worst thing in the world that could happen" would be for the Soviet Union to dominate the oil supplies of the free world through the strategic gulf.

He showed little sympathy for the concerns expressed during the lengthy but so far inconclusive debate on Capitol Hill about the plan to reflag and protect the Kuwaiti vessels.

"The situation in Congress is that they are in betwixt and between . . . . They can't make up their minds," said Shultz. He said President Reagan had "to decide something, and he has."

A sometimes passionate debate in Congress has so far failed to produce a consensus, with key votes postponed last week in Senate and House committees. Democratic leaders said late last week they did not know whether they can forge agreement on a resolution that can win widespread support.

Some of the measures introduced in Congress would stop the reflagging of the Kuwaiti ships and others call for the plan to be delayed or for Kuwaiti shipping to be protected other than by U.S. Navy ships. A reflection of the uncertainty was a draft resolution prepared for debate in the House Foreign Affairs Committee. The resolution said that "neither proceeding with reflagging or withdrawing the proposal advances United States interests."

{For example, Senate Minority Leader Robert J. Dole (R-Kan.), who is considered a leading candidate for the Republican presidential nomination, told the Iowa chapter of the Veterans of Foreign Wars in Des Moines that the United States should maintain a presence in the gulf, but that reflagging the Kuwaiti tankers makes little "military sense," United Press International reported.}

Shultz's strongly worded comments indicated that the administration is determined to move ahead on its own schedule. He said U.S. naval forces are now being assembled in and near the Persian Gulf and that protection for the reflagged ships is likely to begin in the first half of July.

There had been rumors and some published reports before Shultz's television appearance yesterday that he had private misgivings about the reflagging of the Kuwaiti ships. Shultz had been out of Washington on trips to Venice, Iceland, Asia and the Pacific for nearly three weeks while the reflagging debate picked up steam. Yesterday's interview was his first chance since returning last Thursday to express his attitude publicly.

On a related front, Shultz said "a strong diplomatic effort" is under way to persuade the U.N. Security Council to impose sanctions against Iran or Iraq if either of those nations ignores a cease-fire demand that recently won the support of the council's five permanent members.

State Department sources said intensive consultations on the sanctions resolution began last week at the United Nations and that China, as previously reported, remains the most important roadblock to agreement. The position of the Soviet Union is also not completely clear, the sources said, although Moscow is thought likely to agree to an arms embargo or other sanctions against Iran if it rejects the U.N. call for a cease-fire and return of its forces to international boundaries.

The United States and other governments believe Iraq will accept the cease-fire request. Iranian officials have stated in recent days they will reject it.

Shultz, addressing a variety of questions in the television interview, also said:

He found some of the recent revelations about the Iran-contra affair to be "sickening." Under questioning, he said he was referring to testimony that "people who were representing themselves as in some way speaking for America" were indicating that the United States would intervene in the case of radical Shiite prisoners being held by Kuwait.

According to testimony before the joint Senate-House committee, businessman Albert A. Hakim discussed possible freedom for the prisoners in Kuwait with an Iranian official last October in the context of an "arms for hostages" arrangement.

Both he and Assistant Secretary of State Elliott Abrams were "lied to" about U.S. knowledge or complicity in the mission of Eugene Hasenfus, whose cargo plane was shot down over Nicaragua last October. Shultz continued to defend Abrams against congressional attack, saying he is "doing a very good job."