President Reagan failed to order a formal intelligence assessment of the dangers of his Persian Gulf policy, did not consult his political advisers about domestic consequences and first consulted Congress almost a week after the key decision had been made to protect Kuwaiti tankers, according to congressional leaders.

As a result, Reagan's hopes for bipartisan support appear to be dashed, and the plan to place 11 Kuwaiti oil tankers under the protection of the American flag is about to begin without strong backing on Capitol Hill from Democrats or Republicans.

Administration officials continue to insist that they repeatedly sought to consult key congressional committees about the plan but that, as Secretary of State George P. Shultz put it, "at the time we couldn't even get members of Congress to listen as we tried to brief them."

However, the administration's chronology -- released June 15 -- shows that U.S. officials made all the important decisions in January and February, and the process was speeded up when they discovered in late February that the Soviet Union had agreed to reflag five Kuwaiti tankers. Officials gained Reagan's approval of the plan in the first week of March and formally told Kuwait on March 7 that the United States would protect the 11 tankers.

Five days later, the administration made its first offer to brief the Senate and House Middle East subcommittees on the plan. Staffers from the two panels actually were briefed on March 19, according to the administration chronology.

The first high-level administration briefings were given on March 30 and 31, three weeks after Kuwait had been informed, when Assistant Secretary of State Richard W. Murphy met privately with various House and Senate subcommittees.

Presenting Congress with a fait accompli has infuriated the Democratic leadership and placed the administration's allies -- many of whom are as upset as the Democrats -- in an embarrassing position.

"The failure to consult with the Congress prior to a commitment has placed the administration and the Congress in an awkward position," Sen. Sam Nunn (D-Ga.), chairman of the Senate Armed Services Committee, said in a report last Monday to Senate Majority Leader Robert C. Byrd (D-W.Va.). "The administration has made a public commitment to Kuwait but is unable to secure congressional support for its initiative."

The debate raises questions about how the Reagan administration is making key foreign policy decisions under the new White House team led by chief of staff Howard H. Baker Jr. and national security adviser Frank C. Carlucci. It also raises questions about how and why the administration continues to deal with Congress in such a confrontational style over difficult foreign policy issues.

Senate and House members are calling on the administration to set up some kind of procedure for regular consultations on potentially controversial foreign policy commitments to establish a broader bipartisan base for risky initiatives.Lack of Consultation Conceded

Administration officials, while insisting that the president has the prerogative to make foreign policy, concede serious mistakes were made in dealing with Congress on the Kuwaiti reflagging plan.

"I can't say the administration has done the best possible job of explaining {the Kuwaiti decision}. Obviously, they haven't," one senior administration official said.

Another senior official also acknowledged that there had not been enough consultation with Congress at critical points during the policy-making process: "That's how this whole thing got out of control."

But these officials note that even after consulations with key committees got under way after mid-March, little interest or opposition was expressed. Only after an Iraqi plane attacked the USS Stark on May 17 in the Persian Gulf did the Kuwait reflagging plan grab the attention of Congress, they noted.

Other White House sources said one reason for the confusion was that Baker did not take over from Donald T. Regan until March 2. It then took him several weeks to get organized.

By then, all the important decisions had been made, largely by Carlucci and his aides who were pressing a new "activist" policy to show U.S. support for moderate Arab allies following revelations of secret U.S. arms shipments to Iran.

The lack of coordination, and sometimes outright disagreement, between political advisers in the White House and the National Security Council staff is nothing new to the Reagan administration. Former chiefs of staff James A. Baker III, Regan and now Howard Baker have all expressed periodic exasperation at what they viewed as politically insensitive moves by the national security team.

This tension reached new depths when Regan and then-national security adviser Robert C. McFarlane were serving together in late 1985 and the two were hardly speaking. The Regan team often complained, particularly after the Iran-contra scandal broke in November, that they did not have enough "control" over the National Security Council apparatus.

Last November, Regan was talking privately to his aides about ways to achieve such control. Nothing was done, however, because the Iran-contra affair mushroomed and Regan left office in February.

The main White House problem in the Kuwait reflagging plan seems to have been a lack of coordination, although there clearly have been differing views between Reagan's political and foreign policy advisers over how far to go in consulting Congress.

When key decisions were being made in January and February, the president was recovering from prostate surgery and Regan was busy fighting to keep his job. No one at the White House was focusing on the political implications of risking a military confrontation with Iran in the Persian Gulf.

Baker and his staff arrived as the administration was conveying its formal offer to Kuwait. "This whole process began before we got here," said a senior White House official on the Baker side of the White House.Weinberger Opposed Invoking Act

The reflagging plan might have sailed through Congress with little opposition had the Stark not been hit. Once that happened, the consultation process began unraveling as the White House was hit with "what-if questions," the Baker aide said.

In the aftermath, the more politically sensitive of Reagan's advisers, including chief of staff Baker and Treasury Secretary James Baker, argued that Congress should be informed under the 1973 War Powers Resolution. This would have requiring regular consultations and periodic congressional approval of the continuing use of U.S. warships to escort Kuwaiti tankers in the gulf.

But Defense Secretary Caspar W. Weinberger, backed by Shultz and lawyers from the State and Defense departments, opposed invoking the act and convinced Reagan it was not "legally" necessary. That decision set the stage for the confrontation with Congress.

Making matters worse for the White House, key congressional leaders, such Rep. Les Aspin (D-Wis.), chairman of the House Armed Services Committee, discovered that the administration had ordered no formal interagency assessment of the risks in sending U.S. warships to protect the tankers of a nation Iran regards as anything but "neutral" in its war with Iraq.

This left the impression that the administration had acted in haste before weighing the dangers of confronting Iran.

"The intelligence community was never asked for any specific analysis of the threat before the reflagging policy was adopted," Aspin charged in a June 19 statement after a closed-door briefing with Central Intelligence Agency analysts. "There was no assessment from the intelligence community that said, 'If you reflag {Kuwaiti tankers}, this is how things might change.' "

That assessment was completed only recently, according to congressional sources.

White House officials said the long meeting Reagan held last Tuesday with Democratic leaders was a first attempt to salve the wounds inflicted on Congress.

But congressional leaders said much more is needed, and the consulting process with Congress under the Reagan administration needs to be overhauled.

A House Foreign Affairs Committee draft resolution on the Kuwait reflagging plan suggests that the White House establish "an executive-legislative consultative group" that would hold "informal but regular meetings" on the formulation and implementation of all major foreign policy initiatives.

Sen. Richard G. Lugar (R-Ind.), a former Senate Foreign Relations Committee chairman, said in an interview that he agrees some such consultative body needs to be set up. "We really need to have a procedure," he said.

He said that the procedure the White House is supposed to follow in consulting with the Senate and House select committees on intelligence before initiating any covert action might provide a model for executive-congressional consultations over other foreign policy initiatives.Raised Issue With President

The Senate and House majority and minority leaders, plus the leaders of the two Armed Services and Foreign Relations committees could be included, he said, in "a fixed pattern" of consultation on any "substantive change" in foreign policy.

Lugar said that he and Byrd had raised the issue with Reagan of the need for such consultations at the time of the U.S. attack on Libya in April 1986. Reagan called in congressional leaders to inform them the attack was about to occur, but had not consulted them earlier.

Nothing has come of their appeal, Lugar said, noting that the president's defense of his constitutional right to formulate foreign policy without the impingement of Congress has now become "a classic problem."

But the days when a president can alone decide "substantive changes" in U.S. foreign policy and expect automatic bipartisan support "are over," he warned.