Seven months after taking over as President Reagan's national security affairs adviser, Vice Adm. John M. Poindexter has become the object of intensifying criticism from White House colleagues for his management of arms control, the space program and administration foreign policy initiatives in Congress.

Senior officials who have daily contact with Poindexter said in recent interviews that he is well versed in policy matters but complained that he is slow to resolve internal disputes, often overlooks important political considerations and has not mastered the art of explaining complex issues to a president accustomed to dealing in broad concepts rather than details.

For example, the officials said Poindexter had allowed key decisions on the future of the U.S. space program to languish and had failed to anticipate the political outcry following Reagan's May 27 announcement that the United States would no longer be bound by the limits of the unratified SALT II treaty.

In addition some officials said that, before the June 11 presidential news conference, Poindexter had not adequately explained the probable consequences of the SALT II issue to Reagan, whose explanations of his decision contradicted what high-ranking senior administration officials had said about it.

These criticisms -- expressed in interviews by numerous senior administration officials, all of whom requested anonymity -- have persisted even as U.S.-Soviet relations appeared to take a better turn and Reagan expressed optimism that Moscow was beginning to negotiate seriously at the Geneva talks on nuclear and space weapons.

A Poindexter associate said the admiral is successfully dealing with a "full plate" of difficult problems. But other officials said Poindexter appears overloaded and unwilling to delegate, and they expressed dismay at what they described as an increasingly clogged system of paperwork at the National Security Council. "It's like Hoover Dam," one official said.

Poindexter would not comment on these concerns, following his usual practice of shunning the news media. He spurned the recommendation of other White House officials that he conduct a background briefing for reporters on Reagan's SALT II decision -- one of the most important arms control announcements of the president's second term and one that was followed by contradictory administration statements and considerable confusion in the media. Such briefings usually have been conducted in the past by national security affairs advisers or their principal deputies rather than by White House spokesman Larry Speakes, who was instructed to brief on May 27, the day of the SALT II announcement.

Poindexter has told associates he does not believe that briefing the media is an essential part of his job. He has said he views his role primarily as providing information to the president and being an "honest broker" among the strong-willed Cabinet secretaries.

In his unwillingness to explain administration policy to Congress and the media, Poindexter sharply contrasts with Reagan's three previous national security affairs advisers. Richard V. Allen, the first, was a 1980 campaign adviser with strong ties with the conservative movement. He lasted only a year, however, after persistent conflicts with then-Secretary of State Alexander M. Haig Jr.

William P. Clark, his replacement, lacked any foreign policy credentials but brought to the job political experience and an understanding of Reagan, whom he had served as chief of staff in Sacramento. In dealing with Congress, Clark heavily relied on Robert C. McFarlane, a former Senate Armed Services Committee staff member; McFarlane then succeeded Clark when he became secretary of interior.

McFarlane brought both political experience and knowledge of foreign policy issues to the post but was sometimes criticized for being too activist for a president who preached the virtues of Cabinet government. When McFarlane left last December, he recommended his 49-year-old deputy Poindexter as his successor and both Secretary of State George P. Shultz and Defense Secretary Caspar W. Weinberger made it known that they welcomed the idea of a less assertive national security affairs adviser.

Poindexter's strong suit at the time of his appointment appeared to be a capability for managing military crises. Reagan praised Poindexter's performance in directing U.S. forces in the interception of the Achille Lauro hijackers last October, when the admiral was still McFarlane's deputy. Poindexter also coordinated the U.S. military response to Libya in the Gulf of Sidra exercises and the subsequent bombing in April of Libyan leader Moammar Gadhafi's headquarters in retaliation for a West Berlin terrorist attack.

He has also taken the unusual step of remaining on active duty while holding the job.

But Poindexter's military crisis management skill has not been evident in dealing with sensitive political situations, officials say. Poindexter has acknowledged some of these difficulties to other officials, saying that he has been severely hampered recently by the absence of his respected deputy, Donald R. Fortier, a former assistant to House Foreign Affairs Committee Chairman Lee H. Hamilton (D-Ind.).

Fortier, who is seriously ill, had played a critical role in dealing with Congress and in anticipating political problems for the White House on national security issues, officials said.

"Fortier provided a buoyancy factor, and without him, they are sinking," said a senior official. "Poindexter has to do a lot of things he has no experience doing."

In recent weeks, Poindexter has attempted to improve his relations with Capitol Hill by increasing frequency of his meetings with members of Congress, including one last Friday to fashion a new administration approach to aiding the Nicaraguan rebels. He also began weekly breakfasts with White House chief of staff Donald T. Regan about five weeks ago aimed at bettering their working relationship, officials said.

One of the first signs of strain to become public was over the space program. A special interagency group had been established after the space shuttle Challenger tragedy to study both the civilian and national security aspects of the space program.

The expectation was that this group would give the president options on such issues as building a replacement shuttle orbiter, coping with the backlog of commercial and government satellites, dealing with the need for additional unmanned rockets and financing the space program in the future, officials said.

But the result was "gridlock," as one official put it, because of conflict between the National Aeronautics and Space Administration and the Defense Department, a conflict Poindexter did not resolve. "The group was supposed to report in 30 days," said one White House official familiar with the issue. "The presidential Rogers Commission was supposed to report in 120 days. But the Rogers Commission came in first."

Only when, in mid-May, Regan questioned the need for a fourth orbiter did the process move forward, officials said.

The episode that has generated the most criticism of Poindexter in the White House was Reagan's announcement that the United States would no longer be bound by the limits in the SALT II treaty because of alleged Soviet violations. Reagan said he would take into account Soviet arms-control policies over the next several months before deciding whether to exceed the SALT II restrictions when the 131st B52 bomber is armed with air-launched cruise missiles later this year.

The officials said they devoted extra attention to the issue in preparing Reagan for his June 11 news conference, realizing that his comments would be read closely by the Soviets, U.S. allies and critics in Congress.

According to a participant, Poindexter -- who has been described by some officials as relatively disinterested and uninformed about arms control -- gave Reagan a "confused" explanation of what could happen when the United States exceeded the limits on missile launchers in the unratified SALT II treaty.

The president emerged from this briefing apparently under the impression that the decision to abandon the limits had yet to be made. When Reagan was asked at the news conference why he had made the SALT II decision at this time, he responded, "didn't make it now," leaving what aides said was an unintended impression he might return to the SALT II limits.

The next day Speakes attempted to clear up the confusion by announcing that the SALT II limits "no longer exist." Two days later Reagan gave a clear explanation to journalists of what he had done on SALT II -- after a briefing by Regan that Poindexter did not attend.

White House officials also expressed concern that Poindexter has not paid sufficient attention to likely political consequences of the SALT II decision. Although Shultz and some other officials anticipated a strong negative reaction from Congress and the allies, Poindexter seemed surprised by the extent of the criticism, officials said. One key official said Poindexter erred by not preparing follow-up action that would have deflected some of that criticism.

Poindexter was not alone in the White House in failing to anticipate the political outcry against the president's SALT II statement. But as pressure grows on Capitol Hill and in Europe for a new U.S. accord on arms control with the Soviets, officials say that Poindexter appears to be fulfilling his reputation as a manager of military crises rather than an architect of political solutions.